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ConcurrentDictionary<TKey, TValue> Class

Represents a thread-safe collection of key-value pairs that can be accessed by multiple threads concurrently.

System.Object
  System.Collections.Concurrent.ConcurrentDictionary<TKey, TValue>

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

[SerializableAttribute]
[ComVisibleAttribute(false)]
[HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, 
	ExternalThreading = true)]
public class ConcurrentDictionary<TKey, TValue> : IDictionary<TKey, TValue>, 
	ICollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, 
	IDictionary, ICollection, IEnumerable

Type Parameters

TKey

The type of the keys in the dictionary.

TValue

The type of the values in the dictionary.

The ConcurrentDictionary<TKey, TValue> type exposes the following members.

  NameDescription
Public methodConcurrentDictionary<TKey, TValue>()Initializes a new instance of the ConcurrentDictionary<TKey, TValue> class that is empty, has the default concurrency level, has the default initial capacity, and uses the default comparer for the key type.
Public methodConcurrentDictionary<TKey, TValue>(IEnumerable<KeyValuePair<TKey, TValue>>)Initializes a new instance of the ConcurrentDictionary<TKey, TValue> class that contains elements copied from the specified IEnumerable<KeyValuePair<TKey, TValue>>, has the default concurrency level, has the default initial capacity, and uses the default comparer for the key type.
Public methodConcurrentDictionary<TKey, TValue>(IEqualityComparer<TKey>)Initializes a new instance of the ConcurrentDictionary<TKey, TValue> class that is empty, has the default concurrency level and capacity, and uses the specified IEqualityComparer<TKey>.
Public methodConcurrentDictionary<TKey, TValue>(IEnumerable<KeyValuePair<TKey, TValue>>, IEqualityComparer<TKey>)Initializes a new instance of the ConcurrentDictionary<TKey, TValue> class that contains elements copied from the specified IEnumerable, has the default concurrency level, has the default initial capacity, and uses the specified IEqualityComparer<TKey>.
Public methodConcurrentDictionary<TKey, TValue>(Int32, Int32)Initializes a new instance of the ConcurrentDictionary<TKey, TValue> class that is empty, has the specified concurrency level and capacity, and uses the default comparer for the key type.
Public methodConcurrentDictionary<TKey, TValue>(Int32, IEnumerable<KeyValuePair<TKey, TValue>>, IEqualityComparer<TKey>)Initializes a new instance of the ConcurrentDictionary<TKey, TValue> class that contains elements copied from the specified IEnumerable, and uses the specified IEqualityComparer<TKey>.
Public methodConcurrentDictionary<TKey, TValue>(Int32, Int32, IEqualityComparer<TKey>)Initializes a new instance of the ConcurrentDictionary<TKey, TValue> class that is empty, has the specified concurrency level, has the specified initial capacity, and uses the specified IEqualityComparer<TKey>.
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  NameDescription
Public propertyCountGets the number of key/value pairs contained in the ConcurrentDictionary<TKey, TValue>.
Public propertyIsEmptyGets a value that indicates whether the ConcurrentDictionary<TKey, TValue> is empty.
Public propertyItemGets or sets the value associated with the specified key.
Public propertyKeysGets a collection containing the keys in the Dictionary<TKey, TValue>.
Public propertyValuesGets a collection containing the values in the Dictionary<TKey, TValue>.
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  NameDescription
Public methodAddOrUpdate(TKey, Func<TKey, TValue>, Func<TKey, TValue, TValue>)Uses the specified functions to add a key/value pair to the ConcurrentDictionary<TKey, TValue> if the key does not already exist, or updates a key/value pair in the ConcurrentDictionary<TKey, TValue> if the key already exists.
Public methodAddOrUpdate(TKey, TValue, Func<TKey, TValue, TValue>)Adds a key/value pair to the ConcurrentDictionary<TKey, TValue> if the key does not already exist, or uses the specified function to update a key/value pair in the ConcurrentDictionary<TKey, TValue> if the key already exists.
Public methodClearRemoves all keys and values from the ConcurrentDictionary<TKey, TValue>.
Public methodContainsKeyDetermines whether the ConcurrentDictionary<TKey, TValue> contains the specified key.
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetEnumeratorReturns an enumerator that iterates through the ConcurrentDictionary<TKey, TValue>.
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetOrAdd(TKey, Func<TKey, TValue>)Uses the specified function to add a key/value pair to the ConcurrentDictionary<TKey, TValue> if the key does not already exist.
Public methodGetOrAdd(TKey, TValue)Adds a key/value pair to the ConcurrentDictionary<TKey, TValue> if the key does not already exist.
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToArrayCopies the key and value pairs stored in the ConcurrentDictionary<TKey, TValue> to a new array.
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodTryAddAttempts to add the specified key and value to the ConcurrentDictionary<TKey, TValue>.
Public methodTryGetValueAttempts to get the value associated with the specified key from the ConcurrentDictionary<TKey, TValue>.
Public methodTryRemoveAttempts to remove and return the value with the specified key from the ConcurrentDictionary<TKey, TValue>.
Public methodTryUpdateCompares the existing value for the specified key with a specified value, and if they are equal, updates the key with a third value.
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  NameDescription
Public Extension MethodAggregate<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, KeyValuePair<TKey, TValue>, KeyValuePair<TKey, TValue>>)Overloaded. Applies an accumulator function over a sequence. (Defined by Enumerable.)
Public Extension MethodAggregate<KeyValuePair<TKey, TValue>, TAccumulate>(TAccumulate, Func<TAccumulate, KeyValuePair<TKey, TValue>, TAccumulate>)Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value. (Defined by Enumerable.)
Public Extension MethodAggregate<KeyValuePair<TKey, TValue>, TAccumulate, TResult>(TAccumulate, Func<TAccumulate, KeyValuePair<TKey, TValue>, TAccumulate>, Func<TAccumulate, TResult>)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.)
Public Extension MethodAll<KeyValuePair<TKey, TValue>>Determines whether all elements of a sequence satisfy a condition. (Defined by Enumerable.)
Public Extension MethodAny<KeyValuePair<TKey, TValue>>()Overloaded. Determines whether a sequence contains any elements. (Defined by Enumerable.)
Public Extension MethodAny<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)Overloaded. Determines whether any element of a sequence satisfies a condition. (Defined by Enumerable.)
Public Extension MethodAsEnumerable<KeyValuePair<TKey, TValue>>Returns the input typed as IEnumerable<T>. (Defined by Enumerable.)
Public Extension MethodAsParallel()Overloaded. Enables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension MethodAsParallel<KeyValuePair<TKey, TValue>>()Overloaded. Enables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension MethodAsQueryable()Overloaded. Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
Public Extension MethodAsQueryable<KeyValuePair<TKey, TValue>>()Overloaded. Converts a generic IEnumerable<T> to a generic IQueryable<T>. (Defined by Queryable.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Decimal>>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Double>>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int32>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Int32>>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int64>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Int64>>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Single>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Single>>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Double>)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.)
Public Extension MethodAverage<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Decimal>)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.)
Public Extension MethodCast<TResult>Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
Public Extension MethodConcat<KeyValuePair<TKey, TValue>>Concatenates two sequences. (Defined by Enumerable.)
Public Extension MethodContains<KeyValuePair<TKey, TValue>>(KeyValuePair<TKey, TValue>)Overloaded. Determines whether a sequence contains a specified element by using the default equality comparer. (Defined by Enumerable.)
Public Extension MethodContains<KeyValuePair<TKey, TValue>>(KeyValuePair<TKey, TValue>, IEqualityComparer<KeyValuePair<TKey, TValue>>)Overloaded. Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
Public Extension MethodCount<KeyValuePair<TKey, TValue>>()Overloaded. Returns the number of elements in a sequence. (Defined by Enumerable.)
Public Extension MethodCount<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)Overloaded. Returns a number that represents how many elements in the specified sequence satisfy a condition. (Defined by Enumerable.)
Public Extension MethodDefaultIfEmpty<KeyValuePair<TKey, TValue>>()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.)
Public Extension MethodDefaultIfEmpty<KeyValuePair<TKey, TValue>>(KeyValuePair<TKey, TValue>)Overloaded. Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty. (Defined by Enumerable.)
Public Extension MethodDistinct<KeyValuePair<TKey, TValue>>()Overloaded. Returns distinct elements from a sequence by using the default equality comparer to compare values. (Defined by Enumerable.)
Public Extension MethodDistinct<KeyValuePair<TKey, TValue>>(IEqualityComparer<KeyValuePair<TKey, TValue>>)Overloaded. Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
Public Extension MethodElementAt<KeyValuePair<TKey, TValue>>Returns the element at a specified index in a sequence. (Defined by Enumerable.)
Public Extension MethodElementAtOrDefault<KeyValuePair<TKey, TValue>>Returns the element at a specified index in a sequence or a default value if the index is out of range. (Defined by Enumerable.)
Public Extension MethodExcept<KeyValuePair<TKey, TValue>>(IEnumerable<KeyValuePair<TKey, TValue>>)Overloaded. Produces the set difference of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.)
Public Extension MethodExcept<KeyValuePair<TKey, TValue>>(IEnumerable<KeyValuePair<TKey, TValue>>, IEqualityComparer<KeyValuePair<TKey, TValue>>)Overloaded. Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
Public Extension MethodFirst<KeyValuePair<TKey, TValue>>()Overloaded. Returns the first element of a sequence. (Defined by Enumerable.)
Public Extension MethodFirst<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)Overloaded. Returns the first element in a sequence that satisfies a specified condition. (Defined by Enumerable.)
Public Extension MethodFirstOrDefault<KeyValuePair<TKey, TValue>>()Overloaded. Returns the first element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.)
Public Extension MethodFirstOrDefault<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)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.)
Public Extension MethodGroupBy<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>)Overloaded. Groups the elements of a sequence according to a specified key selector function. (Defined by Enumerable.)
Public Extension MethodGroupBy<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>, IEqualityComparer<TKey>)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.)
Public Extension MethodGroupBy<KeyValuePair<TKey, TValue>, TKey, TElement>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<KeyValuePair<TKey, TValue>, TElement>)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.)
Public Extension MethodGroupBy<KeyValuePair<TKey, TValue>, TKey, TResult>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<TKey, IEnumerable<KeyValuePair<TKey, TValue>>, TResult>)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.)
Public Extension MethodGroupBy<KeyValuePair<TKey, TValue>, TKey, TElement>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<KeyValuePair<TKey, TValue>, TElement>, IEqualityComparer<TKey>)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.)
Public Extension MethodGroupBy<KeyValuePair<TKey, TValue>, TKey, TResult>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<TKey, IEnumerable<KeyValuePair<TKey, TValue>>, TResult>, IEqualityComparer<TKey>)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.)
Public Extension MethodGroupBy<KeyValuePair<TKey, TValue>, TKey, TElement, TResult>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<KeyValuePair<TKey, TValue>, TElement>, Func<TKey, IEnumerable<TElement>, TResult>)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.)
Public Extension MethodGroupBy<KeyValuePair<TKey, TValue>, TKey, TElement, TResult>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<KeyValuePair<TKey, TValue>, TElement>, Func<TKey, IEnumerable<TElement>, TResult>, IEqualityComparer<TKey>)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.)
Public Extension MethodGroupJoin<KeyValuePair<TKey, TValue>, TInner, TKey, TResult>(IEnumerable<TInner>, Func<KeyValuePair<TKey, TValue>, TKey>, Func<TInner, TKey>, Func<KeyValuePair<TKey, TValue>, IEnumerable<TInner>, TResult>)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.)
Public Extension MethodGroupJoin<KeyValuePair<TKey, TValue>, TInner, TKey, TResult>(IEnumerable<TInner>, Func<KeyValuePair<TKey, TValue>, TKey>, Func<TInner, TKey>, Func<KeyValuePair<TKey, TValue>, IEnumerable<TInner>, TResult>, IEqualityComparer<TKey>)Overloaded. Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer<T> is used to compare keys. (Defined by Enumerable.)
Public Extension MethodIntersect<KeyValuePair<TKey, TValue>>(IEnumerable<KeyValuePair<TKey, TValue>>)Overloaded. Produces the set intersection of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.)
Public Extension MethodIntersect<KeyValuePair<TKey, TValue>>(IEnumerable<KeyValuePair<TKey, TValue>>, IEqualityComparer<KeyValuePair<TKey, TValue>>)Overloaded. Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
Public Extension MethodJoin<KeyValuePair<TKey, TValue>, TInner, TKey, TResult>(IEnumerable<TInner>, Func<KeyValuePair<TKey, TValue>, TKey>, Func<TInner, TKey>, Func<KeyValuePair<TKey, TValue>, TInner, TResult>)Overloaded. Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys. (Defined by Enumerable.)
Public Extension MethodJoin<KeyValuePair<TKey, TValue>, TInner, TKey, TResult>(IEnumerable<TInner>, Func<KeyValuePair<TKey, TValue>, TKey>, Func<TInner, TKey>, Func<KeyValuePair<TKey, TValue>, TInner, TResult>, IEqualityComparer<TKey>)Overloaded. Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer<T> is used to compare keys. (Defined by Enumerable.)
Public Extension MethodLast<KeyValuePair<TKey, TValue>>()Overloaded. Returns the last element of a sequence. (Defined by Enumerable.)
Public Extension MethodLast<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)Overloaded. Returns the last element of a sequence that satisfies a specified condition. (Defined by Enumerable.)
Public Extension MethodLastOrDefault<KeyValuePair<TKey, TValue>>()Overloaded. Returns the last element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.)
Public Extension MethodLastOrDefault<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)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.)
Public Extension MethodLongCount<KeyValuePair<TKey, TValue>>()Overloaded. Returns an Int64 that represents the total number of elements in a sequence. (Defined by Enumerable.)
Public Extension MethodLongCount<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)Overloaded. Returns an Int64 that represents how many elements in a sequence satisfy a condition. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>()Overloaded. Returns the maximum value in a generic sequence. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Decimal>>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Double>>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Double value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int32>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int32 value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Int32>>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int64>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int64 value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Int64>>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Single>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Single value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Single>>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Single value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Double>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Double value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Decimal>)Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Decimal value. (Defined by Enumerable.)
Public Extension MethodMax<KeyValuePair<TKey, TValue>, TResult>(Func<KeyValuePair<TKey, TValue>, TResult>)Overloaded. Invokes a transform function on each element of a generic sequence and returns the maximum resulting value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>()Overloaded. Returns the minimum value in a generic sequence. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Decimal>>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Double>>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Double value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int32>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int32 value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Int32>>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int64>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int64 value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Int64>>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Single>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Single value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Single>>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Single value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Double>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Double value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Decimal>)Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Decimal value. (Defined by Enumerable.)
Public Extension MethodMin<KeyValuePair<TKey, TValue>, TResult>(Func<KeyValuePair<TKey, TValue>, TResult>)Overloaded. Invokes a transform function on each element of a generic sequence and returns the minimum resulting value. (Defined by Enumerable.)
Public Extension MethodOfType<TResult>Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
Public Extension MethodOrderBy<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>)Overloaded. Sorts the elements of a sequence in ascending order according to a key. (Defined by Enumerable.)
Public Extension MethodOrderBy<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>, IComparer<TKey>)Overloaded. Sorts the elements of a sequence in ascending order by using a specified comparer. (Defined by Enumerable.)
Public Extension MethodOrderByDescending<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>)Overloaded. Sorts the elements of a sequence in descending order according to a key. (Defined by Enumerable.)
Public Extension MethodOrderByDescending<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>, IComparer<TKey>)Overloaded. Sorts the elements of a sequence in descending order by using a specified comparer. (Defined by Enumerable.)
Public Extension MethodReverse<KeyValuePair<TKey, TValue>>Inverts the order of the elements in a sequence. (Defined by Enumerable.)
Public Extension MethodSelect<KeyValuePair<TKey, TValue>, TResult>(Func<KeyValuePair<TKey, TValue>, TResult>)Overloaded. Projects each element of a sequence into a new form. (Defined by Enumerable.)
Public Extension MethodSelect<KeyValuePair<TKey, TValue>, TResult>(Func<KeyValuePair<TKey, TValue>, Int32, TResult>)Overloaded. Projects each element of a sequence into a new form by incorporating the element's index. (Defined by Enumerable.)
Public Extension MethodSelectMany<KeyValuePair<TKey, TValue>, TResult>(Func<KeyValuePair<TKey, TValue>, IEnumerable<TResult>>)Overloaded. Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence. (Defined by Enumerable.)
Public Extension MethodSelectMany<KeyValuePair<TKey, TValue>, TResult>(Func<KeyValuePair<TKey, TValue>, Int32, IEnumerable<TResult>>)Overloaded. Projects each element of a sequence to an IEnumerable<T>, 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.)
Public Extension MethodSelectMany<KeyValuePair<TKey, TValue>, TCollection, TResult>(Func<KeyValuePair<TKey, TValue>, Int32, IEnumerable<TCollection>>, Func<KeyValuePair<TKey, TValue>, TCollection, TResult>)Overloaded. Projects each element of a sequence to an IEnumerable<T>, 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.)
Public Extension MethodSelectMany<KeyValuePair<TKey, TValue>, TCollection, TResult>(Func<KeyValuePair<TKey, TValue>, IEnumerable<TCollection>>, Func<KeyValuePair<TKey, TValue>, TCollection, TResult>)Overloaded. Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. (Defined by Enumerable.)
Public Extension MethodSequenceEqual<KeyValuePair<TKey, TValue>>(IEnumerable<KeyValuePair<TKey, TValue>>)Overloaded. Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type. (Defined by Enumerable.)
Public Extension MethodSequenceEqual<KeyValuePair<TKey, TValue>>(IEnumerable<KeyValuePair<TKey, TValue>>, IEqualityComparer<KeyValuePair<TKey, TValue>>)Overloaded. Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
Public Extension MethodSingle<KeyValuePair<TKey, TValue>>()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.)
Public Extension MethodSingle<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)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.)
Public Extension MethodSingleOrDefault<KeyValuePair<TKey, TValue>>()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.)
Public Extension MethodSingleOrDefault<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)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.)
Public Extension MethodSkip<KeyValuePair<TKey, TValue>>Bypasses a specified number of elements in a sequence and then returns the remaining elements. (Defined by Enumerable.)
Public Extension MethodSkipWhile<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. (Defined by Enumerable.)
Public Extension MethodSkipWhile<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int32, Boolean>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Decimal>>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Double>>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int32>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Int32>>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int64>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Int64>>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Single>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Nullable<Single>>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Double>)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.)
Public Extension MethodSum<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Decimal>)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.)
Public Extension MethodTake<KeyValuePair<TKey, TValue>>Returns a specified number of contiguous elements from the start of a sequence. (Defined by Enumerable.)
Public Extension MethodTakeWhile<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)Overloaded. Returns elements from a sequence as long as a specified condition is true. (Defined by Enumerable.)
Public Extension MethodTakeWhile<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int32, Boolean>)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.)
Public Extension MethodToArray<KeyValuePair<TKey, TValue>>Creates an array from a IEnumerable<T>. (Defined by Enumerable.)
Public Extension MethodToDictionary<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>)Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function. (Defined by Enumerable.)
Public Extension MethodToDictionary<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>, IEqualityComparer<TKey>)Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function and key comparer. (Defined by Enumerable.)
Public Extension MethodToDictionary<KeyValuePair<TKey, TValue>, TKey, TElement>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<KeyValuePair<TKey, TValue>, TElement>)Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to specified key selector and element selector functions. (Defined by Enumerable.)
Public Extension MethodToDictionary<KeyValuePair<TKey, TValue>, TKey, TElement>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<KeyValuePair<TKey, TValue>, TElement>, IEqualityComparer<TKey>)Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function. (Defined by Enumerable.)
Public Extension MethodToList<KeyValuePair<TKey, TValue>>Creates a List<T> from an IEnumerable<T>. (Defined by Enumerable.)
Public Extension MethodToLookup<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>)Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function. (Defined by Enumerable.)
Public Extension MethodToLookup<KeyValuePair<TKey, TValue>, TKey>(Func<KeyValuePair<TKey, TValue>, TKey>, IEqualityComparer<TKey>)Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function and key comparer. (Defined by Enumerable.)
Public Extension MethodToLookup<KeyValuePair<TKey, TValue>, TKey, TElement>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<KeyValuePair<TKey, TValue>, TElement>)Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to specified key selector and element selector functions. (Defined by Enumerable.)
Public Extension MethodToLookup<KeyValuePair<TKey, TValue>, TKey, TElement>(Func<KeyValuePair<TKey, TValue>, TKey>, Func<KeyValuePair<TKey, TValue>, TElement>, IEqualityComparer<TKey>)Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function. (Defined by Enumerable.)
Public Extension MethodUnion<KeyValuePair<TKey, TValue>>(IEnumerable<KeyValuePair<TKey, TValue>>)Overloaded. Produces the set union of two sequences by using the default equality comparer. (Defined by Enumerable.)
Public Extension MethodUnion<KeyValuePair<TKey, TValue>>(IEnumerable<KeyValuePair<TKey, TValue>>, IEqualityComparer<KeyValuePair<TKey, TValue>>)Overloaded. Produces the set union of two sequences by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
Public Extension MethodWhere<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Boolean>)Overloaded. Filters a sequence of values based on a predicate. (Defined by Enumerable.)
Public Extension MethodWhere<KeyValuePair<TKey, TValue>>(Func<KeyValuePair<TKey, TValue>, Int32, Boolean>)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.)
Public Extension MethodZip<KeyValuePair<TKey, TValue>, TSecond, TResult>Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results. (Defined by Enumerable.)
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  NameDescription
Explicit interface implemetationPrivate methodICollection<KeyValuePair<TKey, TValue>>.AddAdds an item to the collection.
Explicit interface implemetationPrivate methodICollection<KeyValuePair<TKey, TValue>>.ContainsGets whether the ICollection contains an element with the specified key.
Explicit interface implemetationPrivate methodICollection<KeyValuePair<TKey, TValue>>.CopyToCopies the elements of the ICollection to an array, starting at the specified array index.
Explicit interface implemetationPrivate methodICollection.CopyToCopies the elements of the ICollection to an array, starting at the specified array index.
Explicit interface implemetationPrivate propertyICollection<KeyValuePair<TKey, TValue>>.IsReadOnlyGets a value indicating whether the ICollection is read-only.
Explicit interface implemetationPrivate propertyICollection.IsSynchronizedGets a value indicating whether access to the ICollection is synchronized with the SyncRoot.
Explicit interface implemetationPrivate methodICollection<KeyValuePair<TKey, TValue>>.RemoveRemoves the specified key/value pair from the collection.
Explicit interface implemetationPrivate propertyICollection.SyncRootGets an object that can be used to synchronize access to the ICollection. This property is not supported.
Explicit interface implemetationPrivate methodIDictionary<TKey, TValue>.AddAdds the specified key and value to the IDictionary<TKey, TValue>.
Explicit interface implemetationPrivate methodIDictionary.AddAdds the specified key and value to the dictionary.
Explicit interface implemetationPrivate methodIDictionary.ContainsGets whether the IDictionary<TKey, TValue> contains an element with the specified key.
Explicit interface implemetationPrivate methodIDictionary.GetEnumeratorProvides an IDictionaryEnumerator for the IDictionary<TKey, TValue>.
Explicit interface implemetationPrivate propertyIDictionary.IsFixedSizeGets a value indicating whether the IDictionary<TKey, TValue> has a fixed size.
Explicit interface implemetationPrivate propertyIDictionary.IsReadOnlyGets a value indicating whether the IDictionary<TKey, TValue> is read-only.
Explicit interface implemetationPrivate propertyIDictionary.ItemGets or sets the value associated with the specified key.
Explicit interface implemetationPrivate propertyIDictionary.KeysGets an ICollection containing the keys of the IDictionary<TKey, TValue>.
Explicit interface implemetationPrivate methodIDictionary<TKey, TValue>.RemoveRemoves the element with the specified key from the IDictionary<TKey, TValue>.
Explicit interface implemetationPrivate methodIDictionary.RemoveRemoves the element with the specified key from the IDictionary.
Explicit interface implemetationPrivate propertyIDictionary.ValuesGets an ICollection containing the values in the IDictionary.
Explicit interface implemetationPrivate methodIEnumerable.GetEnumeratorReturns an enumerator that iterates through the ConcurrentDictionary<TKey, TValue>.
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Like the System.Collections.Generic.Dictionary<TKey, TValue> class, ConcurrentDictionary<TKey, TValue> implements the IDictionary<TKey, TValue> interface. In addition, ConcurrentDictionary<TKey, TValue> provides several methods for adding or updating key/value pairs in the dictionary, as described in the following table.

To do this

Use this method

Usage notes

Add a new key to the dictionary, if it doesn’t already exist in the dictionary

TryAdd

This method adds the specified key/value pair, if the key doesn’t currently exist in the dictionary. The method returns true or false depending on whether the new pair was added.

Update the value for an existing key in the dictionary, if that key has a specific value

TryUpdate

This method checks whether the key has a specified value, and if it does, updates the key with a new value. It's similar to the CompareExchange method, except that it's used for dictionary elements.

Store a key/value pair in the dictionary unconditionally, and overwrite the value of a key that already exists

The indexer’s setter: dictionary[key] = newValue

Add a key/value pair to the dictionary, or if the key already exists, update the value for the key based on the key’s existing value

AddOrUpdate

—or—

AddOrUpdate

AddOrUpdate accepts the key and two delegates. It uses the first delegate if the key doesn’t exist in the dictionary; it accepts the key and returns the value that should be added for the key. It uses the second delegate if the key does exist; it accepts the key and its current value, and it returns the new value that should be set for the key.

AddOrUpdate accepts the key, a value to add, and the update delegate. This is the same as the previous overload, except that it doesn't use a delegate to add a key.

Get the value for a key in the dictionary, adding the value to the dictionary and returning it if the key doesn’t exist

GetOrAdd

—or—

GetOrAdd

These overloads provide lazy initialization for a key/value pair in the dictionary, adding the value only if it’s not there.

GetOrAdd takes the value to be added if the key doesn’t exist.

GetOrAdd takes a delegate that will generate the value if the key doesn’t exist.

All these operations are atomic and are thread-safe with regards to all other operations on the ConcurrentDictionary<TKey, TValue> class. The only exceptions are the methods that accept a delegate, that is, AddOrUpdate and GetOrAdd. For modifications and write operations to the dictionary, ConcurrentDictionary<TKey, TValue> uses fine-grained locking to ensure thread safety. (Read operations on the dictionary are performed in a lock-free manner.) However, delegates for these methods are called outside the locks to avoid the problems that can arise from executing unknown code under a lock. Therefore, the code executed by these delegates is not subject to the atomicity of the operation.

NoteNote

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: Synchronization | ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

The following example shows how to construct a ConcurrentDictionary<TKey, TValue>:



class CD_Ctor
{
        // Demonstrates:
        //      ConcurrentDictionary<TKey, TValue> ctor(concurrencyLevel, initialCapacity)
        //      ConcurrentDictionary<TKey, TValue>[TKey]
        static void Main()
        {
            // We know how many items we want to insert into the ConcurrentDictionary.
            // So set the initial capacity to some prime number above that, to ensure that
            // the ConcurrentDictionary does not need to be resized while initializing it.
            int NUMITEMS = 64;
            int initialCapacity = 101;

            // The higher the concurrencyLevel, the higher the theoretical number of operations
            // that could be performed concurrently on the ConcurrentDictionary.  However, global
            // operations like resizing the dictionary take longer as the concurrencyLevel rises. 
            // For the purposes of this example, we'll compromise at numCores * 2.
            int numProcs = Environment.ProcessorCount;
            int concurrencyLevel = numProcs * 2;

            // Construct the dictionary with the desired concurrencyLevel and initialCapacity
            ConcurrentDictionary<int, int> cd = new ConcurrentDictionary<int, int>(concurrencyLevel, initialCapacity);

            // Initialize the dictionary
            for (int i = 0; i < NUMITEMS; i++) cd[i] = i * i;

            Console.WriteLine("The square of 23 is {0} (should be {1})", cd[23], 23 * 23);
        }
}


.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

All public and protected members of ConcurrentDictionary<TKey, TValue> are thread-safe and may be used concurrently from multiple threads.

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