Dictionary Class
 

Represents a collection of keys and values.

To browse the .NET Framework source code for this type, see the Reference Source.

Namespace:   System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)

SystemObject
  System.Collections.GenericDictionary
     System.ServiceModelMessageQuerySet

[SerializableAttribute]
[ComVisibleAttribute(false)]
public class Dictionary<TKey, TValue> : IDictionary<TKey, TValue>, 
	ICollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, 
	IEnumerable, IDictionary, ICollection, IReadOnlyDictionary<TKey, TValue>, 
	IReadOnlyCollection<KeyValuePair<TKey, TValue>>, ISerializable, 
	IDeserializationCallback
generic<typename TKey, typename TValue>
[SerializableAttribute]
[ComVisibleAttribute(false)]
public ref class Dictionary : IDictionary<TKey, TValue>, ICollection<KeyValuePair<TKey, TValue>>, 
	IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable, IDictionary, 
	ICollection, IReadOnlyDictionary<TKey, TValue>, IReadOnlyCollection<KeyValuePair<TKey, TValue>>, 
	ISerializable, IDeserializationCallback
[<SerializableAttribute>]
[<ComVisibleAttribute(false)>]
type Dictionary<'TKey, 'TValue> = 
    class
        interface IDictionary<'TKey, 'TValue>
        interface ICollection<KeyValuePair<'TKey, 'TValue>>
        interface IEnumerable<KeyValuePair<'TKey, 'TValue>>
        interface IEnumerable
        interface IDictionary
        interface ICollection
        interface IReadOnlyDictionary<'TKey, 'TValue>
        interface IReadOnlyCollection<KeyValuePair<'TKey, 'TValue>>
        interface ISerializable
        interface IDeserializationCallback
    end
<SerializableAttribute>
<ComVisibleAttribute(False)>
Public Class Dictionary(Of TKey, TValue)
	Implements IDictionary(Of TKey, TValue), ICollection(Of KeyValuePair(Of TKey, TValue)),
	IEnumerable(Of KeyValuePair(Of TKey, TValue)), IEnumerable, IDictionary,
	ICollection, IReadOnlyDictionary(Of TKey, TValue), IReadOnlyCollection(Of KeyValuePair(Of TKey, TValue)),
	ISerializable, IDeserializationCallback

Type Parameters

TKey

The type of the keys in the dictionary.

TValue

The type of the values in the dictionary.

NameDescription
System_CAPS_pubmethod Dictionary

Initializes a new instance of the Dictionary class that is empty, has the default initial capacity, and uses the default equality comparer for the key type.

System_CAPS_pubmethod Dictionary

Initializes a new instance of the Dictionary class that contains elements copied from the specified IDictionary and uses the default equality comparer for the key type.

System_CAPS_pubmethod Dictionary

Initializes a new instance of the Dictionary class that contains elements copied from the specified IDictionary and uses the specified IEqualityComparer.

System_CAPS_pubmethod Dictionary

Initializes a new instance of the Dictionary class that is empty, has the default initial capacity, and uses the specified IEqualityComparer.

System_CAPS_pubmethod Dictionary

Initializes a new instance of the Dictionary class that is empty, has the specified initial capacity, and uses the default equality comparer for the key type.

System_CAPS_pubmethod Dictionary

Initializes a new instance of the Dictionary class that is empty, has the specified initial capacity, and uses the specified IEqualityComparer.

System_CAPS_protmethod Dictionary

Initializes a new instance of the Dictionary class with serialized data.

NameDescription
System_CAPS_pubproperty

Gets the IEqualityComparer that is used to determine equality of keys for the dictionary.

System_CAPS_pubproperty

Gets the number of key/value pairs contained in the Dictionary.

System_CAPS_pubproperty

Gets or sets the value associated with the specified key.

System_CAPS_pubproperty

Gets a collection containing the keys in the Dictionary.

System_CAPS_pubproperty

Gets a collection containing the values in the Dictionary.

NameDescription
System_CAPS_pubmethod Add

Adds the specified key and value to the dictionary.

System_CAPS_pubmethod Clear

Removes all keys and values from the Dictionary.

System_CAPS_pubmethod ContainsKey

Determines whether the Dictionary contains the specified key.

System_CAPS_pubmethod ContainsValue

Determines whether the Dictionary contains a specific value.

System_CAPS_pubmethod Equals

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethod Finalize

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethod GetEnumerator

Returns an enumerator that iterates through the Dictionary.

System_CAPS_pubmethod GetHashCode

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethod GetObjectData

Implements the System.Runtime.SerializationISerializable interface and returns the data needed to serialize the Dictionary instance.

System_CAPS_pubmethod GetType

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethod MemberwiseClone

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethod OnDeserialization

Implements the System.Runtime.SerializationISerializable interface and raises the deserialization event when the deserialization is complete.

System_CAPS_pubmethod Remove

Removes the value with the specified key from the Dictionary.

System_CAPS_pubmethod ToString

Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubmethod TryGetValue

Gets the value associated with the specified key.

NameDescription
System_CAPS_pubinterface System_CAPS_privmethod ICollectionAdd

Adds the specified value to the ICollection with the specified key.

System_CAPS_pubinterface System_CAPS_privmethod ICollectionContains

Determines whether the ICollection contains a specific key and value.

System_CAPS_pubinterface System_CAPS_privmethod ICollectionCopyTo

Copies the elements of the ICollection to an array of type KeyValuePair, starting at the specified array index.

System_CAPS_pubinterface System_CAPS_privmethod ICollectionRemove

Removes a key and value from the dictionary.

System_CAPS_pubinterface System_CAPS_privmethod IEnumerableGetEnumerator

Returns an enumerator that iterates through the collection.

System_CAPS_pubinterface System_CAPS_privmethod ICollectionCopyTo

Copies the elements of the ICollection to an array, starting at the specified array index.

System_CAPS_pubinterface System_CAPS_privmethod IDictionaryAdd

Adds the specified key and value to the dictionary.

System_CAPS_pubinterface System_CAPS_privmethod IDictionaryContains

Determines whether the IDictionary contains an element with the specified key.

System_CAPS_pubinterface System_CAPS_privmethod IDictionaryGetEnumerator
System_CAPS_pubinterface System_CAPS_privmethod IDictionaryRemove

Removes the element with the specified key from the IDictionary.

System_CAPS_pubinterface System_CAPS_privmethod IEnumerableGetEnumerator

Returns an enumerator that iterates through the collection.

System_CAPS_pubinterface System_CAPS_privproperty

Gets a value indicating whether the dictionary is read-only.

System_CAPS_pubinterface System_CAPS_privproperty

Gets an ICollection containing the keys of the IDictionary.

System_CAPS_pubinterface System_CAPS_privproperty

Gets an ICollection containing the values in the IDictionary.

System_CAPS_pubinterface System_CAPS_privproperty

Gets a collection containing the keys of the IReadOnlyDictionary.

System_CAPS_pubinterface System_CAPS_privproperty

Gets a collection containing the values of the IReadOnlyDictionary.

System_CAPS_pubinterface System_CAPS_privproperty

Gets a value indicating whether access to the ICollection is synchronized (thread safe).

System_CAPS_pubinterface System_CAPS_privproperty

Gets an object that can be used to synchronize access to the ICollection.

System_CAPS_pubinterface System_CAPS_privproperty

Gets a value indicating whether the IDictionary has a fixed size.

System_CAPS_pubinterface System_CAPS_privproperty

Gets a value indicating whether the IDictionary is read-only.

System_CAPS_pubinterface System_CAPS_privproperty

Gets or sets the value with the specified key.

System_CAPS_pubinterface System_CAPS_privproperty

Gets an ICollection containing the keys of the IDictionary.

System_CAPS_pubinterface System_CAPS_privproperty

Gets an ICollection containing the values in the IDictionary.

NameDescription
System_CAPS_pubmethod Aggregate

Overloaded. Applies an accumulator function over a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Aggregate

Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.(Defined by Enumerable.)

System_CAPS_pubmethod Aggregate

Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.(Defined by Enumerable.)

System_CAPS_pubmethod All

Determines whether all elements of a sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethod Any

Overloaded. Determines whether a sequence contains any elements.(Defined by Enumerable.)

System_CAPS_pubmethod Any

Overloaded. Determines whether any element of a sequence satisfies a condition.(Defined by Enumerable.)

System_CAPS_pubmethod AsEnumerable

Returns the input typed as IEnumerable.(Defined by Enumerable.)

System_CAPS_pubmethod AsParallel

Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.)

System_CAPS_pubmethod AsParallel

Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.)

System_CAPS_pubmethod AsQueryable

Overloaded. Converts an IEnumerable to an IQueryable.(Defined by Queryable.)

System_CAPS_pubmethod AsQueryable

Overloaded. Converts a generic IEnumerable to a generic IQueryable.(Defined by Queryable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Average

Overloaded. Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Cast

Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)

System_CAPS_pubmethod Concat

Concatenates two sequences.(Defined by Enumerable.)

System_CAPS_pubmethod Contains

Overloaded. Determines whether a sequence contains a specified element by using the default equality comparer.(Defined by Enumerable.)

System_CAPS_pubmethod Contains

Overloaded. Determines whether a sequence contains a specified element by using a specified IEqualityComparer.(Defined by Enumerable.)

System_CAPS_pubmethod Count

Overloaded. Returns the number of elements in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Count

Overloaded. Returns a number that represents how many elements in the specified sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethod DefaultIfEmpty

Overloaded. Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty.(Defined by Enumerable.)

System_CAPS_pubmethod DefaultIfEmpty

Overloaded. Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty.(Defined by Enumerable.)

System_CAPS_pubmethod Distinct

Overloaded. Returns distinct elements from a sequence by using the default equality comparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod Distinct

Overloaded. Returns distinct elements from a sequence by using a specified IEqualityComparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod ElementAt

Returns the element at a specified index in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod ElementAtOrDefault

Returns the element at a specified index in a sequence or a default value if the index is out of range.(Defined by Enumerable.)

System_CAPS_pubmethod Except

Overloaded. Produces the set difference of two sequences by using the default equality comparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod Except

Overloaded. Produces the set difference of two sequences by using the specified IEqualityComparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod First

Overloaded. Returns the first element of a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod First

Overloaded. Returns the first element in a sequence that satisfies a specified condition.(Defined by Enumerable.)

System_CAPS_pubmethod FirstOrDefault

Overloaded. Returns the first element of a sequence, or a default value if the sequence contains no elements.(Defined by Enumerable.)

System_CAPS_pubmethod FirstOrDefault

Overloaded. Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.(Defined by Enumerable.)

System_CAPS_pubmethod GroupBy

Overloaded. Groups the elements of a sequence according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethod GroupBy

Overloaded. Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.(Defined by Enumerable.)

System_CAPS_pubmethod GroupBy

Overloaded. Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.(Defined by Enumerable.)

System_CAPS_pubmethod GroupBy

Overloaded. Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.(Defined by Enumerable.)

System_CAPS_pubmethod GroupBy

Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.(Defined by Enumerable.)

System_CAPS_pubmethod GroupBy

Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer.(Defined by Enumerable.)

System_CAPS_pubmethod GroupBy

Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.(Defined by Enumerable.)

System_CAPS_pubmethod GroupBy

Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.(Defined by Enumerable.)

System_CAPS_pubmethod GroupJoin

Overloaded. Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys.(Defined by Enumerable.)

System_CAPS_pubmethod GroupJoin

Overloaded. Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer is used to compare keys.(Defined by Enumerable.)

System_CAPS_pubmethod Intersect

Overloaded. Produces the set intersection of two sequences by using the default equality comparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod Intersect

Overloaded. Produces the set intersection of two sequences by using the specified IEqualityComparer to compare values.(Defined by Enumerable.)

System_CAPS_pubmethod Join

Overloaded. Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys.(Defined by Enumerable.)

System_CAPS_pubmethod Join

Overloaded. Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer is used to compare keys.(Defined by Enumerable.)

System_CAPS_pubmethod Last

Overloaded. Returns the last element of a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Last

Overloaded. Returns the last element of a sequence that satisfies a specified condition.(Defined by Enumerable.)

System_CAPS_pubmethod LastOrDefault

Overloaded. Returns the last element of a sequence, or a default value if the sequence contains no elements.(Defined by Enumerable.)

System_CAPS_pubmethod LastOrDefault

Overloaded. Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.(Defined by Enumerable.)

System_CAPS_pubmethod LongCount

Overloaded. Returns an Int64 that represents the total number of elements in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod LongCount

Overloaded. Returns an Int64 that represents how many elements in a sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Returns the maximum value in a generic sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Decimal value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Double value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int32 value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int64 value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Double value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Single value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Single value.(Defined by Enumerable.)

System_CAPS_pubmethod Max

Overloaded. Invokes a transform function on each element of a generic sequence and returns the maximum resulting value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Returns the minimum value in a generic sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Decimal value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Double value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int32 value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int64 value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Double value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Single value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Single value.(Defined by Enumerable.)

System_CAPS_pubmethod Min

Overloaded. Invokes a transform function on each element of a generic sequence and returns the minimum resulting value.(Defined by Enumerable.)

System_CAPS_pubmethod OfType

Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.)

System_CAPS_pubmethod OrderBy

Overloaded. Sorts the elements of a sequence in ascending order according to a key.(Defined by Enumerable.)

System_CAPS_pubmethod OrderBy

Overloaded. Sorts the elements of a sequence in ascending order by using a specified comparer.(Defined by Enumerable.)

System_CAPS_pubmethod OrderByDescending

Overloaded. Sorts the elements of a sequence in descending order according to a key.(Defined by Enumerable.)

System_CAPS_pubmethod OrderByDescending

Overloaded. Sorts the elements of a sequence in descending order by using a specified comparer.(Defined by Enumerable.)

System_CAPS_pubmethod Reverse

Inverts the order of the elements in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Select

Overloaded. Projects each element of a sequence into a new form.(Defined by Enumerable.)

System_CAPS_pubmethod Select

Overloaded. Projects each element of a sequence into a new form by incorporating the element's index.(Defined by Enumerable.)

System_CAPS_pubmethod SelectMany

Overloaded. Projects each element of a sequence to an IEnumerable and flattens the resulting sequences into one sequence.(Defined by Enumerable.)

System_CAPS_pubmethod SelectMany

Overloaded. Projects each element of a sequence to an IEnumerable, and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element.(Defined by Enumerable.)

System_CAPS_pubmethod SelectMany

Overloaded. Projects each element of a sequence to an IEnumerable, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.(Defined by Enumerable.)

System_CAPS_pubmethod SelectMany

Overloaded. Projects each element of a sequence to an IEnumerable, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. The index of each source element is used in the intermediate projected form of that element.(Defined by Enumerable.)

System_CAPS_pubmethod SequenceEqual

Overloaded. Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type.(Defined by Enumerable.)

System_CAPS_pubmethod SequenceEqual

Overloaded. Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer.(Defined by Enumerable.)

System_CAPS_pubmethod Single

Overloaded. Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Single

Overloaded. Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.(Defined by Enumerable.)

System_CAPS_pubmethod SingleOrDefault

Overloaded. Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.(Defined by Enumerable.)

System_CAPS_pubmethod SingleOrDefault

Overloaded. Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.(Defined by Enumerable.)

System_CAPS_pubmethod Skip

Bypasses a specified number of elements in a sequence and then returns the remaining elements.(Defined by Enumerable.)

System_CAPS_pubmethod SkipWhile

Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.(Defined by Enumerable.)

System_CAPS_pubmethod SkipWhile

Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Sum

Overloaded. Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.(Defined by Enumerable.)

System_CAPS_pubmethod Take

Returns a specified number of contiguous elements from the start of a sequence.(Defined by Enumerable.)

System_CAPS_pubmethod TakeWhile

Overloaded. Returns elements from a sequence as long as a specified condition is true.(Defined by Enumerable.)

System_CAPS_pubmethod TakeWhile

Overloaded. Returns elements from a sequence as long as a specified condition is true. The element's index is used in the logic of the predicate function.(Defined by Enumerable.)

System_CAPS_pubmethod ToArray

Creates an array from a IEnumerable.(Defined by Enumerable.)

System_CAPS_pubmethod ToDictionary

Overloaded. Creates a Dictionary from an IEnumerable according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethod ToDictionary

Overloaded. Creates a Dictionary from an IEnumerable according to a specified key selector function and key comparer.(Defined by Enumerable.)

System_CAPS_pubmethod ToDictionary

Overloaded. Creates a Dictionary from an IEnumerable according to specified key selector and element selector functions.(Defined by Enumerable.)

System_CAPS_pubmethod ToDictionary

Overloaded. Creates a Dictionary from an IEnumerable according to a specified key selector function, a comparer, and an element selector function.(Defined by Enumerable.)

System_CAPS_pubmethod ToList

Creates a List from an IEnumerable.(Defined by Enumerable.)

System_CAPS_pubmethod ToLookup

Overloaded. Creates a Lookup from an IEnumerable according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethod ToLookup

Overloaded. Creates a Lookup from an IEnumerable according to a specified key selector function and key comparer.(Defined by Enumerable.)

System_CAPS_pubmethod ToLookup

Overloaded. Creates a Lookup from an IEnumerable according to specified key selector and element selector functions.(Defined by Enumerable.)

System_CAPS_pubmethod ToLookup

Overloaded. Creates a Lookup from an IEnumerable according to a specified key selector function, a comparer and an element selector function.(Defined by Enumerable.)

System_CAPS_pubmethod Union

Overloaded. Produces the set union of two sequences by using the default equality comparer.(Defined by Enumerable.)

System_CAPS_pubmethod Union

Overloaded. Produces the set union of two sequences by using a specified IEqualityComparer.(Defined by Enumerable.)

System_CAPS_pubmethod Where

Overloaded. Filters a sequence of values based on a predicate.(Defined by Enumerable.)

System_CAPS_pubmethod Where

Overloaded. Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.(Defined by Enumerable.)

System_CAPS_pubmethod Zip

Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results.(Defined by Enumerable.)

System_CAPS_noteNote

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

The Dictionary generic class provides a mapping from a set of keys to a set of values. Each addition to the dictionary consists of a value and its associated key. Retrieving a value by using its key is very fast, close to O(1), because the Dictionary class is implemented as a hash table.

System_CAPS_noteNote

The speed of retrieval depends on the quality of the hashing algorithm of the type specified for TKey.

As long as an object is used as a key in the Dictionary, it must not change in any way that affects its hash value. Every key in a Dictionary must be unique according to the dictionary's equality comparer. A key cannot be null, but a value can be, if the value type TValue is a reference type.

Dictionary requires an equality implementation to determine whether keys are equal. You can specify an implementation of the IEqualityComparer generic interface by using a constructor that accepts a comparer parameter; if you do not specify an implementation, the default generic equality comparer is used. If type TKey implements the SystemIEquatable generic interface, the default equality comparer uses that implementation.

System_CAPS_noteNote

For example, you can use the case-insensitive string comparers provided by the StringComparer class to create dictionaries with case-insensitive string keys.

The capacity of a Dictionary is the number of elements the Dictionary can hold. As elements are added to a Dictionary, the capacity is automatically increased as required by reallocating the internal array.

For very large Dictionary objects, you can increase the maximum capacity to 2 billion elements on a 64-bit system by setting the enabled attribute of the configuration element to true in the run-time environment.

For purposes of enumeration, each item in the dictionary is treated as a KeyValuePair structure representing a value and its key. The order in which the items are returned is undefined.

The foreach statement of the C# language (for each in C++, For Each in Visual Basic) returns an object of the type of the elements in the collection. Since the Dictionary is a collection of keys and values, the element type is not the type of the key or the type of the value. Instead, the element type is a KeyValuePair of the key type and the value type. For example:

foreach( KeyValuePair<string, string> kvp in myDictionary )
{
    Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}
For Each kvp As KeyValuePair(Of String, String) In myDictionary
    Console.WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value)
Next kvp
for each(KeyValuePair<String^, String^> kvp in myDictionary)
{
    Console::WriteLine("Key = {0}, Value = {1}", kvp.Key, kvp.Value);
}

The foreach statement is a wrapper around the enumerator, which allows only reading from the collection, not writing to it.

System_CAPS_noteNote

Because keys can be inherited and their behavior changed, their absolute uniqueness cannot be guaranteed by comparisons using the Equals method.

The following code example creates an empty Dictionary of strings with string keys and uses the Add method to add some elements. The example demonstrates that the Add method throws an ArgumentException when attempting to add a duplicate key.

The example uses the property (the indexer in C#) to retrieve values, demonstrating that a KeyNotFoundException is thrown when a requested key is not present, and showing that the value associated with a key can be replaced.

The example shows how to use the TryGetValue method as a more efficient way to retrieve values if a program often must try key values that are not in the dictionary, and it shows how to use the ContainsKey method to test whether a key exists before calling the Add method.

The example shows how to enumerate the keys and values in the dictionary and how to enumerate the keys and values alone using the property and the property.

Finally, the example demonstrates the Remove method.

using System;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        // Create a new dictionary of strings, with string keys.
        //
        Dictionary<string, string> openWith = 
            new Dictionary<string, string>();

        // Add some elements to the dictionary. There are no 
        // duplicate keys, but some of the values are duplicates.
        openWith.Add("txt", "notepad.exe");
        openWith.Add("bmp", "paint.exe");
        openWith.Add("dib", "paint.exe");
        openWith.Add("rtf", "wordpad.exe");

        // The Add method throws an exception if the new key is 
        // already in the dictionary.
        try
        {
            openWith.Add("txt", "winword.exe");
        }
        catch (ArgumentException)
        {
            Console.WriteLine("An element with Key = \"txt\" already exists.");
        }

        // The Item property is another name for the indexer, so you 
        // can omit its name when accessing elements. 
        Console.WriteLine("For key = \"rtf\", value = {0}.", 
            openWith["rtf"]);

        // The indexer can be used to change the value associated
        // with a key.
        openWith["rtf"] = "winword.exe";
        Console.WriteLine("For key = \"rtf\", value = {0}.", 
            openWith["rtf"]);

        // If a key does not exist, setting the indexer for that key
        // adds a new key/value pair.
        openWith["doc"] = "winword.exe";

        // The indexer throws an exception if the requested key is
        // not in the dictionary.
        try
        {
            Console.WriteLine("For key = \"tif\", value = {0}.", 
                openWith["tif"]);
        }
        catch (KeyNotFoundException)
        {
            Console.WriteLine("Key = \"tif\" is not found.");
        }

        // When a program often has to try keys that turn out not to
        // be in the dictionary, TryGetValue can be a more efficient 
        // way to retrieve values.
        string value = "";
        if (openWith.TryGetValue("tif", out value))
        {
            Console.WriteLine("For key = \"tif\", value = {0}.", value);
        }
        else
        {
            Console.WriteLine("Key = \"tif\" is not found.");
        }

        // ContainsKey can be used to test keys before inserting 
        // them.
        if (!openWith.ContainsKey("ht"))
        {
            openWith.Add("ht", "hypertrm.exe");
            Console.WriteLine("Value added for key = \"ht\": {0}", 
                openWith["ht"]);
        }

        // When you use foreach to enumerate dictionary elements,
        // the elements are retrieved as KeyValuePair objects.
        Console.WriteLine();
        foreach( KeyValuePair<string, string> kvp in openWith )
        {
            Console.WriteLine("Key = {0}, Value = {1}", 
                kvp.Key, kvp.Value);
        }

        // To get the values alone, use the Values property.
        Dictionary<string, string>.ValueCollection valueColl =
            openWith.Values;

        // The elements of the ValueCollection are strongly typed
        // with the type that was specified for dictionary values.
        Console.WriteLine();
        foreach( string s in valueColl )
        {
            Console.WriteLine("Value = {0}", s);
        }

        // To get the keys alone, use the Keys property.
        Dictionary<string, string>.KeyCollection keyColl =
            openWith.Keys;

        // The elements of the KeyCollection are strongly typed
        // with the type that was specified for dictionary keys.
        Console.WriteLine();
        foreach( string s in keyColl )
        {
            Console.WriteLine("Key = {0}", s);
        }

        // Use the Remove method to remove a key/value pair.
        Console.WriteLine("\nRemove(\"doc\")");
        openWith.Remove("doc");

        if (!openWith.ContainsKey("doc"))
        {
            Console.WriteLine("Key \"doc\" is not found.");
        }
    }
}

/* This code example produces the following output:

An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
Key = "tif" is not found.
Key = "tif" is not found.
Value added for key = "ht": hypertrm.exe

Key = txt, Value = notepad.exe
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = winword.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe

Value = notepad.exe
Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = winword.exe
Value = hypertrm.exe

Key = txt
Key = bmp
Key = dib
Key = rtf
Key = doc
Key = ht

Remove("doc")
Key "doc" is not found.
 */
Imports System
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main() 

        ' Create a new dictionary of strings, with string keys.
        '
        Dim openWith As New Dictionary(Of String, String)

        ' Add some elements to the dictionary. There are no 
        ' duplicate keys, but some of the values are duplicates.
        openWith.Add("txt", "notepad.exe")
        openWith.Add("bmp", "paint.exe")
        openWith.Add("dib", "paint.exe")
        openWith.Add("rtf", "wordpad.exe")

        ' The Add method throws an exception if the new key is 
        ' already in the dictionary.
        Try
            openWith.Add("txt", "winword.exe")
        Catch 
            Console.WriteLine("An element with Key = ""txt"" already exists.")
        End Try

        ' The Item property is the default property, so you 
        ' can omit its name when accessing elements. 
        Console.WriteLine("For key = ""rtf"", value = {0}.", _
            openWith("rtf"))

        ' The default Item property can be used to change the value
        ' associated with a key.
        openWith("rtf") = "winword.exe"
        Console.WriteLine("For key = ""rtf"", value = {0}.", _
            openWith("rtf"))

        ' If a key does not exist, setting the default Item property
        ' for that key adds a new key/value pair.
        openWith("doc") = "winword.exe"

        ' The default Item property throws an exception if the requested
        ' key is not in the dictionary.
        Try
            Console.WriteLine("For key = ""tif"", value = {0}.", _
                openWith("tif"))
        Catch 
            Console.WriteLine("Key = ""tif"" is not found.")
        End Try

        ' When a program often has to try keys that turn out not to
        ' be in the dictionary, TryGetValue can be a more efficient 
        ' way to retrieve values.
        Dim value As String = ""
        If openWith.TryGetValue("tif", value) Then
            Console.WriteLine("For key = ""tif"", value = {0}.", value)
        Else
            Console.WriteLine("Key = ""tif"" is not found.")
        End If

        ' ContainsKey can be used to test keys before inserting 
        ' them.
        If Not openWith.ContainsKey("ht") Then
            openWith.Add("ht", "hypertrm.exe")
            Console.WriteLine("Value added for key = ""ht"": {0}", _
                openWith("ht"))
        End If

        ' When you use foreach to enumerate dictionary elements,
        ' the elements are retrieved as KeyValuePair objects.
        Console.WriteLine()
        For Each kvp As KeyValuePair(Of String, String) In openWith
            Console.WriteLine("Key = {0}, Value = {1}", _
                kvp.Key, kvp.Value)
        Next kvp

        ' To get the values alone, use the Values property.
        Dim valueColl As _
            Dictionary(Of String, String).ValueCollection = _
            openWith.Values

        ' The elements of the ValueCollection are strongly typed
        ' with the type that was specified for dictionary values.
        Console.WriteLine()
        For Each s As String In  valueColl
            Console.WriteLine("Value = {0}", s)
        Next s

        ' To get the keys alone, use the Keys property.
        Dim keyColl As _
            Dictionary(Of String, String).KeyCollection = _
            openWith.Keys

        ' The elements of the KeyCollection are strongly typed
        ' with the type that was specified for dictionary keys.
        Console.WriteLine()
        For Each s As String In  keyColl
            Console.WriteLine("Key = {0}", s)
        Next s

        ' Use the Remove method to remove a key/value pair.
        Console.WriteLine(vbLf + "Remove(""doc"")")
        openWith.Remove("doc")

        If Not openWith.ContainsKey("doc") Then
            Console.WriteLine("Key ""doc"" is not found.")
        End If

    End Sub

End Class

' This code example produces the following output:
'
'An element with Key = "txt" already exists.
'For key = "rtf", value = wordpad.exe.
'For key = "rtf", value = winword.exe.
'Key = "tif" is not found.
'Key = "tif" is not found.
'Value added for key = "ht": hypertrm.exe
'
'Key = txt, Value = notepad.exe
'Key = bmp, Value = paint.exe
'Key = dib, Value = paint.exe
'Key = rtf, Value = winword.exe
'Key = doc, Value = winword.exe
'Key = ht, Value = hypertrm.exe
'
'Value = notepad.exe
'Value = paint.exe
'Value = paint.exe
'Value = winword.exe
'Value = winword.exe
'Value = hypertrm.exe
'
'Key = txt
'Key = bmp
'Key = dib
'Key = rtf
'Key = doc
'Key = ht
'
'Remove("doc")
'Key "doc" is not found.
' 
using namespace System;
using namespace System::Collections::Generic;

public ref class Example
{
public:
    static void Main()
    {
        // Create a new dictionary of strings, with string keys.
        //
        Dictionary<String^, String^>^ openWith =
            gcnew Dictionary<String^, String^>();

        // Add some elements to the dictionary. There are no
        // duplicate keys, but some of the values are duplicates.
        openWith->Add("txt", "notepad.exe");
        openWith->Add("bmp", "paint.exe");
        openWith->Add("dib", "paint.exe");
        openWith->Add("rtf", "wordpad.exe");

        // The Add method throws an exception if the new key is
        // already in the dictionary.
        try
        {
            openWith->Add("txt", "winword.exe");
        }
        catch (ArgumentException^)
        {
            Console::WriteLine("An element with Key = \"txt\" already exists.");
        }

        // The Item property is another name for the indexer, so you
        // can omit its name when accessing elements.
        Console::WriteLine("For key = \"rtf\", value = {0}.",
            openWith["rtf"]);

        // The indexer can be used to change the value associated
        // with a key.
        openWith["rtf"] = "winword.exe";
        Console::WriteLine("For key = \"rtf\", value = {0}.",
            openWith["rtf"]);

        // If a key does not exist, setting the indexer for that key
        // adds a new key/value pair.
        openWith["doc"] = "winword.exe";

        // The indexer throws an exception if the requested key is
        // not in the dictionary.
        try
        {
            Console::WriteLine("For key = \"tif\", value = {0}.",
                openWith["tif"]);
        }
        catch (KeyNotFoundException^)
        {
            Console::WriteLine("Key = \"tif\" is not found.");
        }

        // When a program often has to try keys that turn out not to
        // be in the dictionary, TryGetValue can be a more efficient
        // way to retrieve values.
        String^ value = "";
        if (openWith->TryGetValue("tif", value))
        {
            Console::WriteLine("For key = \"tif\", value = {0}.", value);
        }
        else
        {
            Console::WriteLine("Key = \"tif\" is not found.");
        }

        // ContainsKey can be used to test keys before inserting
        // them.
        if (!openWith->ContainsKey("ht"))
        {
            openWith->Add("ht", "hypertrm.exe");
            Console::WriteLine("Value added for key = \"ht\": {0}",
                openWith["ht"]);
        }

        // When you use foreach to enumerate dictionary elements,
        // the elements are retrieved as KeyValuePair objects.
        Console::WriteLine();
        for each( KeyValuePair<String^, String^> kvp in openWith )
        {
            Console::WriteLine("Key = {0}, Value = {1}",
                kvp.Key, kvp.Value);
        }

        // To get the values alone, use the Values property.
        Dictionary<String^, String^>::ValueCollection^ valueColl =
            openWith->Values;

        // The elements of the ValueCollection are strongly typed
        // with the type that was specified for dictionary values.
        Console::WriteLine();
        for each( String^ s in valueColl )
        {
            Console::WriteLine("Value = {0}", s);
        }

        // To get the keys alone, use the Keys property.
        Dictionary<String^, String^>::KeyCollection^ keyColl =
            openWith->Keys;

        // The elements of the KeyCollection are strongly typed
        // with the type that was specified for dictionary keys.
        Console::WriteLine();
        for each( String^ s in keyColl )
        {
            Console::WriteLine("Key = {0}", s);
        }

        // Use the Remove method to remove a key/value pair.
        Console::WriteLine("\nRemove(\"doc\")");
        openWith->Remove("doc");

        if (!openWith->ContainsKey("doc"))
        {
            Console::WriteLine("Key \"doc\" is not found.");
        }
    }
};

int main()
{
    Example::Main();
}

/* This code example produces the following output:

An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
Key = "tif" is not found.
Key = "tif" is not found.
Value added for key = "ht": hypertrm.exe

Key = txt, Value = notepad.exe
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = winword.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe

Value = notepad.exe
Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = winword.exe
Value = hypertrm.exe

Key = txt
Key = bmp
Key = dib
Key = rtf
Key = doc
Key = ht

Remove("doc")
Key "doc" is not found.
 */
Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1

A Dictionary can support multiple readers concurrently, as long as the collection is not modified. Even so, enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with write accesses, the collection must be locked during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

For thread-safe alternatives, see the ConcurrentDictionary class or System.Collections.ImmutableImmutableDictionary class.

Public static (Shared in Visual Basic) members of this type are thread safe.

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