ILookup<TKey, TElement> Interface

 

Defines an indexer, size property, and Boolean search method for data structures that map keys to IEnumerable<T> sequences of values.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

public interface ILookup<TKey, TElement> : IEnumerable<IGrouping<TKey, TElement>>, 
	IEnumerable

Type Parameters

TKey

The type of the keys in the ILookup<TKey, TElement>.

TElement

The type of the elements in the IEnumerable<T> sequences that make up the values in the ILookup<TKey, TElement>.

NameDescription
System_CAPS_pubpropertyCount

Gets the number of key/value collection pairs in the ILookup<TKey, TElement>.

System_CAPS_pubpropertyItem[TKey]

Gets the IEnumerable<T> sequence of values indexed by a specified key.

NameDescription
System_CAPS_pubmethodContains(TKey)

Determines whether a specified key exists in the ILookup<TKey, TElement>.

System_CAPS_pubmethodGetEnumerator()

Returns an enumerator that iterates through the collection.(Inherited from IEnumerable<T>.)

NameDescription
System_CAPS_pubmethodAggregate<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, IGrouping<TKey, TElement>, IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodAggregate<IGrouping<TKey, TElement>, TAccumulate>(TAccumulate, Func<TAccumulate, IGrouping<TKey, TElement>, TAccumulate>)

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

System_CAPS_pubmethodAggregate<IGrouping<TKey, TElement>, TAccumulate, TResult>(TAccumulate, Func<TAccumulate, IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAll<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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

System_CAPS_pubmethodAny<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodAny<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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

System_CAPS_pubmethodAsEnumerable<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodAsParallel()

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

System_CAPS_pubmethodAsParallel<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodAsQueryable()

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

System_CAPS_pubmethodAsQueryable<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodAverage<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodCast<TResult>()

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

System_CAPS_pubmethodConcat<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>)

Concatenates two sequences.(Defined by Enumerable.)

System_CAPS_pubmethodContains<IGrouping<TKey, TElement>>(IGrouping<TKey, TElement>)

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

System_CAPS_pubmethodContains<IGrouping<TKey, TElement>>(IGrouping<TKey, TElement>, IEqualityComparer<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodCount<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodCount<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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

System_CAPS_pubmethodDefaultIfEmpty<IGrouping<TKey, TElement>>()

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_pubmethodDefaultIfEmpty<IGrouping<TKey, TElement>>(IGrouping<TKey, TElement>)

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_pubmethodDistinct<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodDistinct<IGrouping<TKey, TElement>>(IEqualityComparer<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodElementAt<IGrouping<TKey, TElement>>(Int32)

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

System_CAPS_pubmethodElementAtOrDefault<IGrouping<TKey, TElement>>(Int32)

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_pubmethodExcept<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodExcept<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>, IEqualityComparer<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodFirst<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodFirst<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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

System_CAPS_pubmethodFirstOrDefault<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodFirstOrDefault<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodGroupBy<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, TKey>)

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

System_CAPS_pubmethodGroupBy<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodGroupBy<IGrouping<TKey, TElement>, TKey, TElement>(Func<IGrouping<TKey, TElement>, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodGroupBy<IGrouping<TKey, TElement>, TKey, TElement>(Func<IGrouping<TKey, TElement>, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodGroupBy<IGrouping<TKey, TElement>, TKey, TResult>(Func<IGrouping<TKey, TElement>, TKey>, Func<TKey, IEnumerable<IGrouping<TKey, 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.(Defined by Enumerable.)

System_CAPS_pubmethodGroupBy<IGrouping<TKey, TElement>, TKey, TResult>(Func<IGrouping<TKey, TElement>, TKey>, Func<TKey, IEnumerable<IGrouping<TKey, 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. The keys are compared by using a specified comparer.(Defined by Enumerable.)

System_CAPS_pubmethodGroupBy<IGrouping<TKey, TElement>, TKey, TElement, TResult>(Func<IGrouping<TKey, TElement>, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodGroupBy<IGrouping<TKey, TElement>, TKey, TElement, TResult>(Func<IGrouping<TKey, TElement>, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodGroupJoin<IGrouping<TKey, TElement>, TInner, TKey, TResult>(IEnumerable<TInner>, Func<IGrouping<TKey, TElement>, TKey>, Func<TInner, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodGroupJoin<IGrouping<TKey, TElement>, TInner, TKey, TResult>(IEnumerable<TInner>, Func<IGrouping<TKey, TElement>, TKey>, Func<TInner, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodIntersect<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodIntersect<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>, IEqualityComparer<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodJoin<IGrouping<TKey, TElement>, TInner, TKey, TResult>(IEnumerable<TInner>, Func<IGrouping<TKey, TElement>, TKey>, Func<TInner, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodJoin<IGrouping<TKey, TElement>, TInner, TKey, TResult>(IEnumerable<TInner>, Func<IGrouping<TKey, TElement>, TKey>, Func<TInner, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodLast<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodLast<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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

System_CAPS_pubmethodLastOrDefault<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodLastOrDefault<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodLongCount<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodLongCount<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Decimal>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Double>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Int32>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Int64>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Decimal>>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Double>>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Int32>>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Int64>>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Single>>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Single>)

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

System_CAPS_pubmethodMax<IGrouping<TKey, TElement>, TResult>(Func<IGrouping<TKey, TElement>, TResult>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Decimal>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Double>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Int32>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Int64>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Decimal>>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Double>>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Int32>>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Int64>>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Nullable<Single>>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Single>)

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

System_CAPS_pubmethodMin<IGrouping<TKey, TElement>, TResult>(Func<IGrouping<TKey, TElement>, TResult>)

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

System_CAPS_pubmethodOfType<TResult>()

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

System_CAPS_pubmethodOrderBy<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, TKey>)

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

System_CAPS_pubmethodOrderBy<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, TKey>, IComparer<TKey>)

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

System_CAPS_pubmethodOrderByDescending<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, TKey>)

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

System_CAPS_pubmethodOrderByDescending<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, TKey>, IComparer<TKey>)

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

System_CAPS_pubmethodReverse<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodSelect<IGrouping<TKey, TElement>, TResult>(Func<IGrouping<TKey, TElement>, TResult>)

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

System_CAPS_pubmethodSelect<IGrouping<TKey, TElement>, TResult>(Func<IGrouping<TKey, TElement>, Int32, TResult>)

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

System_CAPS_pubmethodSelectMany<IGrouping<TKey, TElement>, TResult>(Func<IGrouping<TKey, TElement>, IEnumerable<TResult>>)

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

System_CAPS_pubmethodSelectMany<IGrouping<TKey, TElement>, TResult>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSelectMany<IGrouping<TKey, TElement>, TCollection, TResult>(Func<IGrouping<TKey, TElement>, IEnumerable<TCollection>>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSelectMany<IGrouping<TKey, TElement>, TCollection, TResult>(Func<IGrouping<TKey, TElement>, Int32, IEnumerable<TCollection>>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSequenceEqual<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>)

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_pubmethodSequenceEqual<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>, IEqualityComparer<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodSingle<IGrouping<TKey, TElement>>()

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_pubmethodSingle<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSingleOrDefault<IGrouping<TKey, TElement>>()

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_pubmethodSingleOrDefault<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSkip<IGrouping<TKey, TElement>>(Int32)

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

System_CAPS_pubmethodSkipWhile<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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_pubmethodSkipWhile<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodSum<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodTake<IGrouping<TKey, TElement>>(Int32)

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

System_CAPS_pubmethodTakeWhile<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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

System_CAPS_pubmethodTakeWhile<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodToArray<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodToDictionary<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, TKey>)

Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethodToDictionary<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodToDictionary<IGrouping<TKey, TElement>, TKey, TElement>(Func<IGrouping<TKey, TElement>, TKey>, Func<IGrouping<TKey, TElement>, TElement>)

Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to specified key selector and element selector functions.(Defined by Enumerable.)

System_CAPS_pubmethodToDictionary<IGrouping<TKey, TElement>, TKey, TElement>(Func<IGrouping<TKey, TElement>, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodToList<IGrouping<TKey, TElement>>()

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

System_CAPS_pubmethodToLookup<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, TKey>)

Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethodToLookup<IGrouping<TKey, TElement>, TKey>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodToLookup<IGrouping<TKey, TElement>, TKey, TElement>(Func<IGrouping<TKey, TElement>, TKey>, Func<IGrouping<TKey, TElement>, TElement>)

Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to specified key selector and element selector functions.(Defined by Enumerable.)

System_CAPS_pubmethodToLookup<IGrouping<TKey, TElement>, TKey, TElement>(Func<IGrouping<TKey, TElement>, TKey>, Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodUnion<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodUnion<IGrouping<TKey, TElement>>(IEnumerable<IGrouping<TKey, TElement>>, IEqualityComparer<IGrouping<TKey, TElement>>)

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

System_CAPS_pubmethodWhere<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, Boolean>)

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

System_CAPS_pubmethodWhere<IGrouping<TKey, TElement>>(Func<IGrouping<TKey, TElement>, 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.)

System_CAPS_pubmethodZip<IGrouping<TKey, TElement>, TSecond, TResult>(IEnumerable<TSecond>, Func<IGrouping<TKey, TElement>, TSecond, TResult>)

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

The type Lookup<TKey, TElement> implements the ILookup<TKey, TElement> interface.

The extension method ToLookup, which can be appended to the end of a LINQ query, returns an object of type ILookup<TKey, TElement>.

The following code example creates an ILookup<TKey, TElement> object and iterates through its contents.

class Package
{
    public string Company { get; set; }
    public double Weight { get; set; }
    public long TrackingNumber { get; set; }
}

public static void ILookupExample()
{
    // Create a list of Packages to put into an ILookup data structure.
    List<Package> packages = new List<Package> { new Package { Company = "Coho Vineyard", Weight = 25.2, TrackingNumber = 89453312L },
                                                 new Package { Company = "Lucerne Publishing", Weight = 18.7, TrackingNumber = 89112755L },
                                                 new Package { Company = "Wingtip Toys", Weight = 6.0, TrackingNumber = 299456122L },
                                                 new Package { Company = "Contoso Pharmaceuticals", Weight = 9.3, TrackingNumber = 670053128L },
                                                 new Package { Company = "Wide World Importers", Weight = 33.8, TrackingNumber = 4665518773L } };

    // Create a Lookup to organize the packages. Use the first character of Company as the key value.
    // Select Company appended to TrackingNumber for each element value in the ILookup object.
    ILookup<char, string> packageLookup = packages.ToLookup(
        p => Convert.ToChar(p.Company.Substring(0, 1)),
        p => p.Company + " " + p.TrackingNumber
        );

    // Iterate through each value in the ILookup and output the contents.
    foreach (var packageGroup in packageLookup)
    {
        // Print the key value.
        Console.WriteLine(packageGroup.Key);
        // Iterate through each value in the collection.
        foreach (string str in packageGroup)
            Console.WriteLine("    {0}", str);
    }

    // This code produces the following output:
    //
    // C
    //     Coho Vineyard 89453312
    //     Contoso Pharmaceuticals 670053128
    // L
    //     Lucerne Publishing 89112755
    // W
    //     Wingtip Toys 299456122
    //     Wide World Importers 4665518773
}

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
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
Return to top
Show: