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Enumerable.GroupBy<TSource, TKey, TResult> Method (IEnumerable<TSource>, Func<TSource, TKey>, Func<TKey, IEnumerable<TSource>, TResult>, IEqualityComparer<TKey>)
.NET Framework (current version)
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.
Assembly: System.Core (in System.Core.dll)
public static IEnumerable<TResult> GroupBy<TSource, TKey, TResult>( this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TKey, IEnumerable<TSource>, TResult> resultSelector, IEqualityComparer<TKey> comparer )
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.
- comparer
-
Type:
System.Collections.Generic.IEqualityComparer<TKey>
An IEqualityComparer<T> to compare keys with.
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.
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
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
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