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Enumerable.Count<'TSource> Method (IEnumerable<'TSource>, Func<'TSource, Boolean>)


Returns a number that represents how many elements in the specified sequence satisfy a condition.

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

static member Count<'TSource> : 
        source:IEnumerable<'TSource> *
        predicate:Func<'TSource, bool> -> int


Type: System.Collections.Generic.IEnumerable<'TSource>

A sequence that contains elements to be tested and counted.

Type: System.Func<'TSource, Boolean>

A function to test each element for a condition.

Return Value

Type: System.Int32

A number that represents how many elements in the sequence satisfy the condition in the predicate function.

Type Parameters


The type of the elements of source.

Exception Condition

source or predicate is null.


The number of elements in source is larger than MaxValue.

If the type of source implements ICollection<'T>, that implementation is used to obtain the count of elements. Otherwise, this method determines the count.

You should use the LongCount<'TSource> method when you expect and want to allow the result to be greater than MaxValue.

In Visual Basic query expression syntax, an Aggregate Into Count() clause translates to an invocation of Count.

The following code example demonstrates how to use Count<'TSource>(IEnumerable<'TSource>, Func<'TSource, Boolean>) to count the elements in an array that satisfy a condition.

No code example is currently available or this language may not be supported.

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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