Enumerable.GroupBy<'TSource, 'TKey, 'TResult> Method (IEnumerable<'TSource>, Func<'TSource, 'TKey>, Func<'TKey, IEnumerable<'TSource>, 'TResult>)
Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.
Assembly: System.Core (in System.Core.dll)
static member GroupBy<'TSource, 'TKey, 'TResult> : source:IEnumerable<'TSource> * keySelector:Func<'TSource, 'TKey> * resultSelector:Func<'TKey, IEnumerable<'TSource>, 'TResult> -> IEnumerable<'TResult>
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.
- resultSelector
-
Type:
System.Func<'TKey, IEnumerable<'TSource>, '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.
- 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, 'TResult>(IEnumerable<'TSource>, Func<'TSource, 'TKey>, Func<'TKey, IEnumerable<'TSource>, 'TResult>) to group the elements of a sequence and 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