Expression.Loop 方法

定义

创建一个 LoopExpression

重载

Loop(Expression)

创建具有给定主体的 LoopExpression

Loop(Expression, LabelTarget)

创建具有给定主体和中断目标的 LoopExpression

Loop(Expression, LabelTarget, LabelTarget)

创建具有给定主体的 LoopExpression

Loop(Expression)

Source:
LoopExpression.cs
Source:
LoopExpression.cs
Source:
LoopExpression.cs

创建具有给定主体的 LoopExpression

public:
 static System::Linq::Expressions::LoopExpression ^ Loop(System::Linq::Expressions::Expression ^ body);
public static System.Linq.Expressions.LoopExpression Loop (System.Linq.Expressions.Expression body);
static member Loop : System.Linq.Expressions.Expression -> System.Linq.Expressions.LoopExpression
Public Shared Function Loop (body As Expression) As LoopExpression

参数

body
Expression

循环体。

返回

创建的 LoopExpression

适用于

Loop(Expression, LabelTarget)

Source:
LoopExpression.cs
Source:
LoopExpression.cs
Source:
LoopExpression.cs

创建具有给定主体和中断目标的 LoopExpression

public:
 static System::Linq::Expressions::LoopExpression ^ Loop(System::Linq::Expressions::Expression ^ body, System::Linq::Expressions::LabelTarget ^ break);
public static System.Linq.Expressions.LoopExpression Loop (System.Linq.Expressions.Expression body, System.Linq.Expressions.LabelTarget break);
public static System.Linq.Expressions.LoopExpression Loop (System.Linq.Expressions.Expression body, System.Linq.Expressions.LabelTarget? break);
static member Loop : System.Linq.Expressions.Expression * System.Linq.Expressions.LabelTarget -> System.Linq.Expressions.LoopExpression
Public Shared Function Loop (body As Expression, break As LabelTarget) As LoopExpression

参数

body
Expression

循环体。

break
LabelTarget

循环体使用的中断目标。

返回

创建的 LoopExpression

示例

以下示例演示如何创建包含 LoopExpression 对象的块表达式。

// Add the following directive to the file:
// using System.Linq.Expressions;

// Creating a parameter expression.
ParameterExpression value = Expression.Parameter(typeof(int), "value");

// Creating an expression to hold a local variable.
ParameterExpression result = Expression.Parameter(typeof(int), "result");

// Creating a label to jump to from a loop.
LabelTarget label = Expression.Label(typeof(int));

// Creating a method body.
BlockExpression block = Expression.Block(
    new[] { result },
    Expression.Assign(result, Expression.Constant(1)),
        Expression.Loop(
           Expression.IfThenElse(
               Expression.GreaterThan(value, Expression.Constant(1)),
               Expression.MultiplyAssign(result,
                   Expression.PostDecrementAssign(value)),
               Expression.Break(label, result)
           ),
       label
    )
);

// Compile and run an expression tree.
int factorial = Expression.Lambda<Func<int, int>>(block, value).Compile()(5);

Console.WriteLine(factorial);

// This code example produces the following output:
//
// 120
' Add the following directive to the file:
' Imports System.Linq.Expressions  

' Creating a parameter expression.
Dim value As ParameterExpression =
    Expression.Parameter(GetType(Integer), "value")

' Creating an expression to hold a local variable. 
Dim result As ParameterExpression =
    Expression.Parameter(GetType(Integer), "result")

' Creating a label to jump to from a loop.
Dim label As LabelTarget = Expression.Label(GetType(Integer))

' Creating a method body.
Dim block As BlockExpression = Expression.Block(
    New ParameterExpression() {result},
    Expression.Assign(result, Expression.Constant(1)),
    Expression.Loop(
        Expression.IfThenElse(
            Expression.GreaterThan(value, Expression.Constant(1)),
            Expression.MultiplyAssign(result,
                Expression.PostDecrementAssign(value)),
            Expression.Break(label, result)
        ),
        label
    )
)

' Compile an expression tree and return a delegate.
Dim factorial As Integer =
    Expression.Lambda(Of Func(Of Integer, Integer))(block, value).Compile()(5)

Console.WriteLine(factorial)

' This code example produces the following output:
'
' 120

适用于

Loop(Expression, LabelTarget, LabelTarget)

Source:
LoopExpression.cs
Source:
LoopExpression.cs
Source:
LoopExpression.cs

创建具有给定主体的 LoopExpression

public:
 static System::Linq::Expressions::LoopExpression ^ Loop(System::Linq::Expressions::Expression ^ body, System::Linq::Expressions::LabelTarget ^ break, System::Linq::Expressions::LabelTarget ^ continue);
public static System.Linq.Expressions.LoopExpression Loop (System.Linq.Expressions.Expression body, System.Linq.Expressions.LabelTarget break, System.Linq.Expressions.LabelTarget continue);
public static System.Linq.Expressions.LoopExpression Loop (System.Linq.Expressions.Expression body, System.Linq.Expressions.LabelTarget? break, System.Linq.Expressions.LabelTarget? continue);
static member Loop : System.Linq.Expressions.Expression * System.Linq.Expressions.LabelTarget * System.Linq.Expressions.LabelTarget -> System.Linq.Expressions.LoopExpression
Public Shared Function Loop (body As Expression, break As LabelTarget, continue As LabelTarget) As LoopExpression

参数

body
Expression

循环体。

break
LabelTarget

循环体使用的中断目标。

continue
LabelTarget

循环体使用的继续目标。

返回

创建的 LoopExpression

适用于