Enumerable.LongCount(Of TSource) Method (IEnumerable(Of TSource), Func(Of TSource, Boolean))
Returns an Int64 that represents how many elements in a sequence satisfy a condition.
Assembly: System.Core (in System.Core.dll)
<ExtensionAttribute> Public Shared Function LongCount(Of TSource) ( source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean) ) As Long
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.
Type Parameters
- TSource
The type of the elements of source.
| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is null. |
| OverflowException | The number of matching elements exceeds MaxValue. |
Use this method rather than Count(Of TSource) when you expect the result to be greater than MaxValue.
In Visual Basic query expression syntax, an Aggregate Into LongCount() clause translates to an invocation of LongCount(Of TSource).
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. MsgBox("There are " & count & " animals over age " & Age) End Sub ' This code produces the following output: ' ' There are 2 animals over age 3
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1