Queryable.All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 方法

定义

确定序列中的所有元素是否都满足条件。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 Boolean

类型参数

TSource

source 的元素类型。The type of the elements of source.

参数

source
IQueryable<TSource>

要测试其元素是否满足条件的序列。A sequence whose elements to test for a condition.

predicate
Expression<Func<TSource,Boolean>>

用于测试每个元素是否满足条件的函数。A function to test each element for a condition.

返回

如果源序列中的每个元素都通过指定谓词中的测试,或者序列为空,则为 true;否则为 falsetrue if every element of the source sequence passes the test in the specified predicate, or if the sequence is empty; otherwise, false.

异常

sourcepredicatenullsource or predicate is null.

示例

下面的代码示例演示如何使用 All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 来确定序列中的所有元素是否都满足条件。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'. 

All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 方法返回的布尔值通常用于 where 子句的谓词(Visual Basic 中的Where 子句)或对 Where 方法的直接调用。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. 下面的示例演示如何使用 All 方法。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

注解

此方法至少具有一个类型 Expression<TDelegate> 的参数,其类型参数为 Func<T,TResult> 类型之一。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 对于这些参数,可以传入 lambda 表达式,并将其编译为 Expression<TDelegate>For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 方法生成一个 MethodCallExpression,它表示作为构造的泛型方法调用 All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 本身。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. 然后,它将 MethodCallExpression 传递到 IQueryProviderExecute<TResult>(Expression) 方法(由 source 参数的 Provider 属性表示)。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

因执行表示调用 All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 的表达式树而发生的查询行为取决于 source 参数类型的实现。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. 预期的行为是确定 source 中的所有元素是否都满足 predicate中的条件。The expected behavior is that it determines if all the elements in source satisfy the condition in predicate.

适用于