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.NET Framework Class Library

Enumerable.All<TSource> Method

Determines whether all elements of a sequence satisfy a condition.

Namespace:  System.Linq
Assemblies:   System.Linq (in System.Linq.dll)
  System.Core (in System.Core.dll)
<ExtensionAttribute> _
Public Shared Function All(Of TSource) ( _
	source As IEnumerable(Of TSource), _
	predicate As Func(Of TSource, Boolean) _
) As Boolean

Type Parameters


The type of the elements of source.


Type: System.Collections.Generic.IEnumerable<TSource>

An IEnumerable<T> that contains the elements to apply the predicate to.

Type: System.Func<TSource, Boolean>

A function to test each element for a condition.

Return Value

Type: System.Boolean
true if every element of the source sequence passes the test in the specified predicate, or if the sequence is empty; otherwise, false.

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. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).
Exception Condition

source or predicate is null.

Note Note

This method does not return all the elements of a collection. Instead, it determines whether all the elements of a collection satisfy a condition.

The enumeration of source is stopped as soon as the result can be determined.

In Visual Basic query expression syntax, an Aggregate Into All() clause translates to an invocation of All<TSource>.

The following code example demonstrates how to use All<TSource> to determine whether all the elements in a sequence satisfy a condition. Variable allStartWithB is true if all the pet names start with "B" or if the pets array is empty.

    Structure Pet
        Public Name As String 
        Public Age As Integer 
    End Structure 

    Sub AllEx()
        ' Create an array of Pets. 
        Dim pets() As Pet = _
            {New Pet With {.Name = "Barley", .Age = 2}, _
             New Pet With {.Name = "Boots", .Age = 4}, _
             New Pet With {.Name = "Whiskers", .Age = 7}}

        ' Determine whether all pet names in the array start with "B". 
        Dim allNames As Boolean = _
            pets.All(Function(ByVal pet) pet.Name.StartsWith("B"))

        ' Display the output. 
        Dim text As String = IIf(allNames, "All", "Not all")
        MsgBox(text & " pet names start with 'B'.")
    End Sub 

    ' This code produces the following output: 
    ' Not all pet names start with 'B'.

The Boolean value that the All<TSource> method returns is typically used in the predicate of a where clause (Where clause in Visual Basic) or a direct call to the Where method. The following example demonstrates this use of the All method.

Structure Pet
    Public Name As String 
    Public Age As Integer 
End Structure 

Structure Person
    Public LastName As String 
    Public Pets() As Pet
End Structure 

Sub AllEx2()
    Dim people As New List(Of Person)(New Person() _
        {New Person With {.LastName = "Haas", _
                          .Pets = New Pet() {New Pet With {.Name = "Barley", .Age = 10}, _
                                             New Pet With {.Name = "Boots", .Age = 14}, _
                                             New Pet With {.Name = "Whiskers", .Age = 6}}}, _
          New Person With {.LastName = "Fakhouri", _
                           .Pets = New Pet() {New Pet With {.Name = "Snowball", .Age = 1}}}, _
          New Person With {.LastName = "Antebi", _
                           .Pets = New Pet() {New Pet With {.Name = "Belle", .Age = 8}}}, _
          New Person With {.LastName = "Philips", _
                           .Pets = New Pet() {New Pet With {.Name = "Sweetie", .Age = 2}, _
                                              New Pet With {.Name = "Rover", .Age = 13}}}})

    ' Determine which people have pets that are all older than 5. 
    Dim names = From person In people _
                Where person.Pets.All(Function(pet) pet.Age > 5) _
                Select person.LastName

    For Each name As String In names

    ' This code produces the following output: 
    ' Haas 
    ' Antebi 

End Sub

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library