Queryable.All(Of TSource) Method (IQueryable(Of TSource), Expression(Of Func(Of TSource, Boolean)))
Determines whether all the elements of a sequence satisfy a condition.
Assembly: System.Core (in System.Core.dll)
<ExtensionAttribute> Public Shared Function All(Of TSource) ( source As IQueryable(Of TSource), predicate As Expression(Of Func(Of TSource, Boolean)) ) As Boolean
Parameters
- source
-
Type:
System.Linq.IQueryable(Of TSource)
A sequence whose elements to test for a condition.
- predicate
-
Type:
System.Linq.Expressions.Expression(Of Func(Of TSource, Boolean))
A function to test each element for a condition.
Return Value
Type: System.Booleantrue if every element of the source sequence passes the test in the specified predicate, or if the sequence is empty; otherwise, false.
Type Parameters
- TSource
The type of the elements of source.
| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is null. |
This method has at least one parameter of type Expression(Of TDelegate) whose type argument is one of the Func(Of T, TResult) types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression(Of TDelegate).
The All(Of TSource)(IQueryable(Of TSource), Expression(Of Func(Of TSource, Boolean))) method generates a MethodCallExpression that represents calling All(Of TSource)(IQueryable(Of TSource), Expression(Of Func(Of TSource, Boolean))) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute(Of TResult)(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.
The query behavior that occurs as a result of executing an expression tree that represents calling All(Of TSource)(IQueryable(Of TSource), Expression(Of Func(Of TSource, Boolean))) depends on the implementation of the source parameter's type. The expected behavior is that it determines if all the elements in source satisfy the condition in predicate.
The following code example demonstrates how to use All(Of TSource)(IQueryable(Of TSource), Expression(Of Func(Of TSource, Boolean))) to determine whether all the elements in a sequence satisfy a condition.
Sub AllEx() ' Create an array of Pets. Dim pets() As Pet = _ {New Pet With {.Name = "Barley", .Age = 10}, _ New Pet With {.Name = "Boots", .Age = 4}, _ New Pet With {.Name = "Whiskers", .Age = 6}} ' Determine whether all pet names in the array start with 'B'. Dim allStartWithB As Boolean = _ pets.AsQueryable().All(Function(ByVal pet) pet.Name.StartsWith("B")) MsgBox(String.Format( _ "{0} pet names start with 'B'.", _ IIf(allStartWithB, "All", "Not all"))) End Sub Public Structure Pet Dim Name As String Dim Age As Integer End Structure ' This code produces the following output: ' ' Not all pet names start with 'B'.
The Boolean value that the All(Of TSource)(IQueryable(Of TSource), Expression(Of Func(Of TSource, Boolean))) method returns is typically used in the predicate of a where clause (Where clause in Visual Basic) or a direct call to the Where(Of TSource) 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.AsQueryable().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
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 7.1
Windows Phone
Available since 8.1