Enumerable::GroupBy<TSource, TKey, TElement, TResult> Method (IEnumerable<TSource>^, Func<TSource, TKey>^, Func<TSource, TElement>^, Func<TKey, IEnumerable<TElement>^, TResult>^)
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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.
Assembly: System.Core (in System.Core.dll)
public: generic<typename TSource, typename TKey, typename TElement, typename TResult> [ExtensionAttribute] static IEnumerable<TResult>^ GroupBy( IEnumerable<TSource>^ source, Func<TSource, TKey>^ keySelector, Func<TSource, TElement>^ elementSelector, Func<TKey, IEnumerable<TElement>^, TResult>^ resultSelector )
Parameters
- source
-
Type:
System.Collections.Generic::IEnumerable<TSource>^
An IEnumerable<T> whose elements to group.
- keySelector
-
Type:
System::Func<TSource, TKey>^
A function to extract the key for each element.
- elementSelector
-
Type:
System::Func<TSource, TElement>^
A function to map each source element to an element in an IGrouping<TKey, TElement>.
- resultSelector
-
Type:
System::Func<TKey, IEnumerable<TElement>^, TResult>^
A function to create a result value from each group.
Return Value
Type: System.Collections.Generic::IEnumerable<TResult>^A collection of elements of type TResult where each element represents a projection over a group and its key.
Type Parameters
- TSource
The type of the elements of source.
- TKey
The type of the key returned by keySelector.
- TElement
The type of the elements in each IGrouping<TKey, TElement>.
- TResult
The type of the result value returned by resultSelector.
In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy.
The following code example demonstrates how to use GroupBy<TSource, TKey, TElement, TResult>(IEnumerable<TSource>^, Func<TSource, TKey>^, Func<TSource, TElement>^, Func<TKey, IEnumerable<TElement>^, TResult>^) to group the projected elements of a sequence and then project a sequence of results of type TResult.
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