Enumerable.LongCount(Of TSource) Method (IEnumerable(Of TSource), Func(Of TSource, Boolean))
Silverlight
Returns an Int64 that represents how many elements in a sequence satisfy a condition.
Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)
'Declaration <ExtensionAttribute> _ Public Shared Function LongCount(Of TSource) ( _ source As IEnumerable(Of TSource), _ predicate As Func(Of TSource, Boolean) _ ) As Long
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- Type: System.Collections.Generic.IEnumerable(Of TSource)
An IEnumerable(Of T) that contains the elements to be counted.
- predicate
- Type: System.Func(Of TSource, Boolean)
A function to test each element for a condition.
Return Value
Type: System.Int64A 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.| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is Nothing. |
| OverflowException | The number of matching elements exceeds MaxValue. |
The following code example demonstrates how to use LongCount(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 Age As Integer End Structure Sub LongCountEx2() ' Create a list of Pet objects. Dim pets As New List(Of Pet)(New Pet() _ {New Pet With {.Name = "Barley", .Age = 8}, _ New Pet With {.Name = "Boots", .Age = 4}, _ New Pet With {.Name = "Whiskers", .Age = 1}}) ' Determine the number of elements in the list ' where the pet's age is greater than a constant value (3). Const Age As Integer = 3 Dim count As Long = _ pets.LongCount(Function(pet) pet.Age > Age) ' Display the result. outputBlock.Text & ="There are " & count & " animals over age " & Age & vbCrLf End Sub ' This code produces the following output: ' ' There are 2 animals over age 3
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
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