GroupBy Method

GroupBy<TSource, TKey, TElement, TResult>(IIndexedSource<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource, TElement>>, Expression<Func<TKey, IEnumerable<TElement>, TResult>>)

Groups the elements of a collection 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.

Declaration

public static IIndexedSource<TResult> GroupBy<TSource, TKey, TElement, TResult>(this IIndexedSource<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector, Expression<Func<TKey, IEnumerable<TElement>, TResult>> resultSelector)

Public Shared Function GroupBy(Of TSource, TKey, TElement, TResult)(source As IIndexedSource(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), elementSelector As Expression(Of Func(Of TSource, TElement)), resultSelector As Expression(Of Func(Of TKey, IEnumerable(Of TElement), TResult))) As IIndexedSource(Of TResult)

Parameters

Type	Name	Description
IIndexedSource<TSource>	source	An IIndexedSource<T> whose elements to group
Expression<Func<TSource, TKey>>	keySelector	A function to extract the key for each element.
Expression<Func<TSource, TElement>>	elementSelector	A function to map each source element to an element in the IGrouping<TKey, TElement>.
Expression<Func<TKey, IEnumerable<TElement>, TResult>>	resultSelector	A function to create a result value from each group.

Returns

Type	Description
IIndexedSource<TResult>	A collection of elements of type TResult where each element represents a projection over a group and its key.

Type Parameters

Name	Description
TSource	The type of the elements of source.
TKey	The type of the key returned by keySelector.
TElement	The type of the elements in the IGrouping<TKey, TElement>.
TResult	The type of the result value returned by resultSelector

GroupBy<TSource, TKey, TElement>(IIndexedSource<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource, TElement>>)

Groups the elements of a collection according to a specified key selector function and projects the elements for each group by using a specified function.

Declaration

public static IIndexedSource<IGrouping<TKey, TElement>> GroupBy<TSource, TKey, TElement>(this IIndexedSource<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TSource, TElement>> elementSelector)

Public Shared Function GroupBy(Of TSource, TKey, TElement)(source As IIndexedSource(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), elementSelector As Expression(Of Func(Of TSource, TElement))) As IIndexedSource(Of IGrouping(Of TKey, TElement))

Parameters

Type	Name	Description
IIndexedSource<TSource>	source	An IIndexedSource<T> whose elements to group
Expression<Func<TSource, TKey>>	keySelector	A function to extract the key for each element.
Expression<Func<TSource, TElement>>	elementSelector	A function to map each source element to an element in the IGrouping<TKey, TElement>.

Returns

Type	Description
IIndexedSource<IGrouping<TKey, TElement>>	A collection of IGrouping<TKey, TElement> objects each containing a collection of objects of type TElement and a key.

Type Parameters

Name	Description
TSource	The type of the elements of source.
TKey	The type of the key returned by keySelector.
TElement	The type of the elements in the IGrouping<TKey, TElement>.

GroupBy<TSource, TKey, TResult>(IIndexedSource<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TKey, IEnumerable<TSource>, TResult>>)

Groups the elements of a collection according to a specified key selector function and creates a result value from each group and its key.

Declaration

public static IIndexedSource<TResult> GroupBy<TSource, TKey, TResult>(this IIndexedSource<TSource> source, Expression<Func<TSource, TKey>> keySelector, Expression<Func<TKey, IEnumerable<TSource>, TResult>> resultSelector)

Public Shared Function GroupBy(Of TSource, TKey, TResult)(source As IIndexedSource(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), resultSelector As Expression(Of Func(Of TKey, IEnumerable(Of TSource), TResult))) As IIndexedSource(Of TResult)

Parameters

Type	Name	Description
IIndexedSource<TSource>	source	An IIndexedSource<T> whose elements to group
Expression<Func<TSource, TKey>>	keySelector	A function to extract the key for each element.
Expression<Func<TKey, IEnumerable<TSource>, TResult>>	resultSelector	A function to create a result value from each group.

Returns

Type	Description
IIndexedSource<TResult>	A collection of elements of type TResult where each element represents a projection over a group and its key.

Type Parameters

Name	Description
TSource	The type of the elements of source.
TKey	The type of the key returned by keySelector.
TResult	The type of the result value returned by resultSelector

GroupBy<TSource, TKey>(IIndexedSource<TSource>, Expression<Func<TSource, TKey>>)

Groups the elements of a collection according to a specified key selector function.

Declaration

public static IIndexedSource<IGrouping<TKey, TSource>> GroupBy<TSource, TKey>(this IIndexedSource<TSource> source, Expression<Func<TSource, TKey>> keySelector)

Public Shared Function GroupBy(Of TSource, TKey)(source As IIndexedSource(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey))) As IIndexedSource(Of IGrouping(Of TKey, TSource))

Parameters

Type	Name	Description
IIndexedSource<TSource>	source	An IIndexedSource<T> whose elements to group
Expression<Func<TSource, TKey>>	keySelector	A function to extract the key for each element.

Returns

Type	Description
IIndexedSource<IGrouping<TKey, TSource>>	A collection of IGrouping<TKey, TElement> objects each containing a sequence of objects and a key.

Type Parameters

Name	Description
TSource	The type of the elements of source.
TKey	The type of the key returned by keySelector.