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)

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

Type Parameters

TSource

The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable(TSource)
A sequence that contains elements to be tested and counted.
predicate
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.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(TSource). When you use instance method syntax to call this method, omit the first parameter.

ExceptionCondition
ArgumentNullException

source or predicate is a null reference (Nothing in Visual Basic).

OverflowException

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 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.

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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