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)
Visual Basic (Declaration)
<ExtensionAttribute> _
Public Shared Function Count(Of TSource) ( _
source As IEnumerable(Of TSource), _
predicate As Func(Of TSource, Boolean) _
) As Integer
Dim source As IEnumerable(Of TSource)
Dim predicate As Func(Of TSource, Boolean)
Dim returnValue As Integer
returnValue = source.Count(predicate)
public static int Count<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate
)
[ExtensionAttribute]
public:
generic<typename TSource>
static int Count(
IEnumerable<TSource>^ source,
Func<TSource, bool>^ predicate
)
JScript does not support generic types or methods.
Type Parameters
- TSource
The type of the elements of source.
Return Value
Type:
System..::.Int32A 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<(Of <(TSource>)>). When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).
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.
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<(Of <(TSource>)>)(IEnumerable<(Of <(TSource>)>), Func<(Of <(TSource, Boolean>)>)) to count the elements in an array that satisfy a condition.
Structure Pet
Public Name As String
Public Vaccinated As Boolean
End Structure
Sub CountEx2()
' Create an array of Pet objects.
Dim pets() As Pet = {New Pet With {.Name = "Barley", .Vaccinated = True}, _
New Pet With {.Name = "Boots", .Vaccinated = False}, _
New Pet With {.Name = "Whiskers", .Vaccinated = False}}
Try
' Count the number of Pets in the array where the Vaccinated property is False.
Dim numberUnvaccinated As Integer = _
pets.Count(Function(p) p.Vaccinated = False)
' Display the output.
MsgBox("There are " & numberUnvaccinated & " unvaccinated animals.")
Catch e As OverflowException
MsgBox("The count is too large to store as an Int32. Try using LongCount() instead.")
End Try
End Sub
' This code produces the following output:
'
' There are 2 unvaccinated animals.
class Pet
{
public string Name { get; set; }
public bool Vaccinated { get; set; }
}
public static void CountEx2()
{
Pet[] pets = { new Pet { Name="Barley", Vaccinated=true },
new Pet { Name="Boots", Vaccinated=false },
new Pet { Name="Whiskers", Vaccinated=false } };
try
{
int numberUnvaccinated = pets.Count(p => p.Vaccinated == false);
Console.WriteLine("There are {0} unvaccinated animals.", numberUnvaccinated);
}
catch (OverflowException)
{
Console.WriteLine("The count is too large to store as an Int32.");
Console.WriteLine("Try using the LongCount() method instead.");
}
}
// This code produces the following output:
//
// There are 2 unvaccinated animals.
Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5
.NET Compact Framework
Supported in: 3.5
XNA Framework
Supported in: 3.0
Reference
Other Resources