Determines whether all elements of a sequence satisfy a condition.
Namespace:
System.Linq
Assembly:
System.Core (in System.Core.dll)
Visual Basic (Declaration)
<ExtensionAttribute> _
Public Shared Function All(Of TSource) ( _
source As IEnumerable(Of TSource), _
predicate As Func(Of TSource, Boolean) _
) As Boolean
Dim source As IEnumerable(Of TSource)
Dim predicate As Func(Of TSource, Boolean)
Dim returnValue As Boolean
returnValue = source.All(predicate)
public static bool All<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate
)
[ExtensionAttribute]
public:
generic<typename TSource>
static bool All(
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..::.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<(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).
| Exception | Condition |
|---|
| ArgumentNullException |
source or predicate is nullNothingnullptra null reference (Nothing in Visual Basic). |
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<(Of <(TSource>)>).
The following code example demonstrates how to use All<(Of <(TSource>)>) to determine whether all the elements in a sequence satisfy a condition.
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'.
class Pet
{
public string Name { get; set; }
public int Age { get; set; }
}
public static void AllEx()
{
// Create an array of Pets.
Pet[] pets = { new Pet { Name="Barley", Age=10 },
new Pet { Name="Boots", Age=4 },
new Pet { Name="Whiskers", Age=6 } };
// Determine whether all pet names
// in the array start with 'B'.
bool allStartWithB = pets.All(pet =>
pet.Name.StartsWith("B"));
Console.WriteLine(
"{0} pet names start with 'B'.",
allStartWithB ? "All" : "Not all");
}
// This code produces the following output:
//
// Not all pet names start with 'B'.
The Boolean value that the All<(Of <(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
Console.WriteLine(name)
Next
' This code produces the following output:
'
' Haas
' Antebi
End Sub
class Pet
{
public string Name { get; set; }
public int Age { get; set; }
}
class Person
{
public string LastName { get; set; }
public Pet[] Pets { get; set; }
}
public static void AllEx2()
{
List<Person> people = new List<Person>
{ new Person { LastName = "Haas",
Pets = new Pet[] { new Pet { Name="Barley", Age=10 },
new Pet { Name="Boots", Age=14 },
new Pet { Name="Whiskers", Age=6 }}},
new Person { LastName = "Fakhouri",
Pets = new Pet[] { new Pet { Name = "Snowball", Age = 1}}},
new Person { LastName = "Antebi",
Pets = new Pet[] { new Pet { Name = "Belle", Age = 8} }},
new Person { LastName = "Philips",
Pets = new Pet[] { new Pet { Name = "Sweetie", Age = 2},
new Pet { Name = "Rover", Age = 13}} }
};
// Determine which people have pets that are all older than 5.
IEnumerable<string> names = from person in people
where person.Pets.All(pet => pet.Age > 5)
select person.LastName;
foreach (string name in names)
{
Console.WriteLine(name);
}
/* This code produces the following output:
*
* Haas
* Antebi
*/
}
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
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