Queryable.All<TSource> Method
Definition
Important
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Determines whether all the elements of a sequence satisfy a condition.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static bool All(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, bool> ^> ^ predicate);public static bool All<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,bool>> predicate);static member All : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, bool>> -> bool<Extension()>
Public Function All(Of TSource) (source As IQueryable(Of TSource), predicate As Expression(Of Func(Of TSource, Boolean))) As BooleanType Parameters
- TSource
The type of the elements of source.
Parameters
- source
- IQueryable<TSource>
A sequence whose elements to test for a condition.
- predicate
- Expression<Func<TSource,Boolean>>
A function to test each element for a condition.
Returns
true if every element of the source sequence passes the test in the specified predicate, or if the sequence is empty; otherwise, false.
Exceptions
source or predicate is null.
Examples
The following code example demonstrates how to use All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) to determine whether all the elements in a sequence satisfy a condition.
class Pet
{
public string Name { get; set; }
public int Age { get; set; }
}
public static void AllEx1()
{
// 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.AsQueryable().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'.
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<TSource>(IQueryable<TSource>, Expression<Func<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 method. The following example demonstrates this use of the All method.
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.AsQueryable().All(pet => pet.Age > 5)
select person.LastName;
foreach (string name in names)
Console.WriteLine(name);
/* This code produces the following output:
*
* Haas
* Antebi
*/
}
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
Remarks
This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.
The All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) method generates a MethodCallExpression that represents calling All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<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<TSource>(IQueryable<TSource>, Expression<Func<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.
