Count Generic Method

public static int Count<TSource> (
	IEnumerable<TSource> source,
	Func<TSource, bool> predicate
)

Not applicable.

Type Parameters

TSource

The type of the elements of source.

Parameters

source

System.Collections.Generic.IEnumerable<(Of T>)

An IEnumerable<(Of T>) that contains the elements to be counted.

predicate

System.Linq.Func<(Of TArg0, TResult>)

A function to test each element for a condition.

Return Value

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

If the type of source implements ICollection<(Of 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.

The following code example demonstrates how to use Count to count the elements in an array that satisfy a condition.

struct Pet
{
    public string Name;
    public bool Vaccinated;
}

public static void CountEx2()
{
    Pet[] pets = { new Pet { Name="Barley", Vaccinated=true },
                   new Pet { Name="Boots", Vaccinated=false },
                   new Pet { Name="Whiskers", Vaccinated=false } };
    int numberUnvaccinated = pets.Count(p => p.Vaccinated == false);
    Console.WriteLine("There are {0} unvaccinated animals.", numberUnvaccinated);
}
/*
 This code produces the following output:

 There are 2 unvaccinated animals.
*/

Windows CE, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP SP2, Windows Vista

The .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

.NET Compact Framework

Reference