Queryable.Any 方法
定义
确定 IQueryable<T> 序列中的任何元素是否都存在或满足条件。Determines whether any element of an IQueryable<T> sequence exists or satisfies a condition.
重载
| Any<TSource>(IQueryable<TSource>) |
确定序列是否包含任何元素。Determines whether a sequence contains any elements. |
| Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) |
确定序列中是否存在任意一个元素满足条件。Determines whether any element of a sequence satisfies a condition. |
Any<TSource>(IQueryable<TSource>)
确定序列是否包含任何元素。Determines whether a sequence contains any elements.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static bool Any(System::Linq::IQueryable<TSource> ^ source);
public static bool Any<TSource> (this System.Linq.IQueryable<TSource> source);
static member Any : System.Linq.IQueryable<'Source> -> bool
<Extension()>
Public Function Any(Of TSource) (source As IQueryable(Of TSource)) 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>
要检查是否为空的序列。A sequence to check for being empty.
返回
如果源序列包含任何元素,则为 true;否则为 false。true if the source sequence contains any elements; otherwise, false.
例外
source 为 null。source is null.
示例
下面的代码示例演示如何使用 Any<TSource>(IQueryable<TSource>) 来确定序列是否包含任何元素。The following code example demonstrates how to use Any<TSource>(IQueryable<TSource>) to determine whether a sequence contains any elements.
List<int> numbers = new List<int> { 1, 2 };
// Determine if the list contains any elements.
bool hasElements = numbers.AsQueryable().Any();
Console.WriteLine("The list {0} empty.",
hasElements ? "is not" : "is");
// This code produces the following output:
//
// The list is not empty.
Dim numbers As New List(Of Integer)(New Integer() {1, 2})
' Determine if the list contains any elements.
Dim hasElements As Boolean = numbers.AsQueryable().Any()
MsgBox(String.Format("The list {0} empty.", _
IIf(hasElements, "is not", "is")))
' This code produces the following output:
'
' The list is not empty.
方法返回的布尔值 Any<TSource>(IQueryable<TSource>) 通常用于 where Where Visual Basic) 中子句 (子句的谓词或对方法的直接调用 Where<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 。The Boolean value that the Any<TSource>(IQueryable<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<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) method. 下面的示例演示如何使用 Any 方法。The following example demonstrates this use of the Any 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 AnyEx2()
{
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 Person { LastName = "Philips",
Pets = new Pet[] { new Pet { Name = "Sweetie", Age = 2},
new Pet { Name = "Rover", Age = 13}} }
};
// Determine which people have a non-empty Pet array.
IEnumerable<string> names = from person in people
where person.Pets.AsQueryable().Any()
select person.LastName;
foreach (string name in names)
Console.WriteLine(name);
/* This code produces the following output:
Haas
Fakhouri
Philips
*/
}
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 AnyEx2()
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 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 a non-empty Pet array.
Dim names = From person In people _
Where person.Pets.AsQueryable().Any() _
Select person.LastName
For Each name As String In names
Console.WriteLine(name)
Next
' This code produces the following output:
'
' Haas
' Fakhouri
' Philips
End Sub
注解
Any<TSource>(IQueryable<TSource>)方法生成一个 MethodCallExpression ,它表示调用 Any<TSource>(IQueryable<TSource>) 自身作为构造的泛型方法。The Any<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Any<TSource>(IQueryable<TSource>) itself as a constructed generic method. 然后,它将传递 MethodCallExpression 给 Execute<TResult>(Expression) IQueryProvider 由参数的属性表示的的方法 Provider source 。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.
由于执行表示调用的表达式树而发生的查询行为 Any<TSource>(IQueryable<TSource>) 取决于参数类型的实现 source 。The query behavior that occurs as a result of executing an expression tree that represents calling Any<TSource>(IQueryable<TSource>) depends on the implementation of the type of the source parameter. 预期的行为是确定是否 source 包含任何元素。The expected behavior is that it determines if source contains any elements.
适用于
Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)
确定序列中是否存在任意一个元素满足条件。Determines whether any element of a sequence satisfies a condition.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static bool Any(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, bool> ^> ^ predicate);
public static bool Any<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,bool>> predicate);
static member Any : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, bool>> -> bool
<Extension()>
Public Function Any(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
如果源序列中存在元素通过了指定谓词中的测试,则为 true;否则为 false。true if any elements in the source sequence pass the test in the specified predicate; otherwise, false.
例外
source 或 predicate 为 null。source or predicate is null.
示例
下面的代码示例演示如何使用Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)以确定序列中是否有任意一个元素满足条件。 The following code example demonstrates how to use Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) to determine whether any element in a sequence satisfies a condition.
class Pet
{
public string Name { get; set; }
public int Age { get; set; }
public bool Vaccinated { get; set; }
}
public static void AnyEx3()
{
// Create an array of Pet objects.
Pet[] pets =
{ new Pet { Name="Barley", Age=8, Vaccinated=true },
new Pet { Name="Boots", Age=4, Vaccinated=false },
new Pet { Name="Whiskers", Age=1, Vaccinated=false } };
// Determine whether any pets over age 1 are also unvaccinated.
bool unvaccinated =
pets.AsQueryable().Any(p => p.Age > 1 && p.Vaccinated == false);
Console.WriteLine(
"There {0} unvaccinated animals over age one.",
unvaccinated ? "are" : "are not any");
}
// This code produces the following output:
//
// There are unvaccinated animals over age one.
Structure Pet
Dim Name As String
Dim Age As Integer
Dim Vaccinated As Boolean
End Structure
Shared Sub AnyEx3()
' Create an array of Pet objects.
Dim pets() As Pet = _
{New Pet With {.Name = "Barley", .Age = 8, .Vaccinated = True}, _
New Pet With {.Name = "Boots", .Age = 4, .Vaccinated = False}, _
New Pet With {.Name = "Whiskers", .Age = 1, .Vaccinated = False}}
' Determine whether any pets over age 1 are also unvaccinated.
Dim unvaccinated As Boolean = _
pets.AsQueryable().Any(Function(p) p.Age > 1 And p.Vaccinated = False)
MsgBox(String.Format( _
"There {0} unvaccinated animals over age one.", _
IIf(unvaccinated, "are", "are not any") _
))
End Sub
' This code produces the following output:
'
' There are unvaccinated animals over age one.
注解
此方法至少具有一个类型为的参数, Expression<TDelegate> 其类型参数为类型之一 Func<T,TResult> 。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>.
Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)方法生成一个 MethodCallExpression ,它表示调用 Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 自身作为构造的泛型方法。The Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) method generates a MethodCallExpression that represents calling Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) itself as a constructed generic method. 然后,它将传递 MethodCallExpression 给 Execute<TResult>(Expression) IQueryProvider 由参数的属性表示的的方法 Provider source 。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.
由于执行表示调用的表达式树而发生的查询行为 Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 取决于参数类型的实现 source 。The query behavior that occurs as a result of executing an expression tree that represents calling Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) depends on the implementation of the type of the source parameter. 预期的行为是确定的任何元素是否 source 满足指定的条件 predicate 。The expected behavior is that it determines if any of the elements of source satisfy the condition specified by predicate.