BlockExpression Sınıf

Tanım

public ref class BlockExpression : System::Linq::Expressions::Expression

public class BlockExpression : System.Linq.Expressions.Expression

type BlockExpression = class
    inherit Expression

Public Class BlockExpression
Inherits Expression

Devralma

Object

Expression

BlockExpression

Örnekler

Aşağıdaki kod örneğinde blok ifadesinin nasıl oluşturulacağı gösterilmektedir. Blok ifadesi iki MethodCallExpression nesneden ve bir nesneden ConstantExpression oluşur.

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

// The block expression allows for executing several expressions sequentually.
// When the block expression is executed,
// it returns the value of the last expression in the sequence.
BlockExpression blockExpr = Expression.Block(
    Expression.Call(
        null,
        typeof(Console).GetMethod("Write", new Type[] { typeof(String) }),
        Expression.Constant("Hello ")
       ),
    Expression.Call(
        null,
        typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
        Expression.Constant("World!")
        ),
    Expression.Constant(42)
);

Console.WriteLine("The result of executing the expression tree:");
// The following statement first creates an expression tree,
// then compiles it, and then executes it.
var result = Expression.Lambda<Func<int>>(blockExpr).Compile()();

// Print out the expressions from the block expression.
Console.WriteLine("The expressions from the block expression:");
foreach (var expr in blockExpr.Expressions)
    Console.WriteLine(expr.ToString());

// Print out the result of the tree execution.
Console.WriteLine("The return value of the block expression:");
Console.WriteLine(result);

// This code example produces the following output:
//
// The result of executing the expression tree:
// Hello World!

// The expressions from the block expression:
// Write("Hello ")
// WriteLine("World!")
// 42

// The return value of the block expression:
// 42

' Add the following directive to your file:
' Imports System.Linq.Expressions

' The block expression enables you to execute several expressions sequentually.
' When the block expression is executed,
' it returns the value of the last expression in the sequence.
Dim blockExpr As BlockExpression = Expression.Block(
    Expression.Call(
        Nothing,
        GetType(Console).GetMethod("Write", New Type() {GetType(String)}),
        Expression.Constant("Hello ")
       ),
    Expression.Call(
        Nothing,
        GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
        Expression.Constant("World!")
        ),
    Expression.Constant(42)
)

Console.WriteLine("The result of executing the expression tree:")
' The following statement first creates an expression tree,
' then compiles it, and then executes it.           
Dim result = Expression.Lambda(Of Func(Of Integer))(blockExpr).Compile()()

' Print the expressions from the block expression.
Console.WriteLine("The expressions from the block expression:")
For Each expr In blockExpr.Expressions
    Console.WriteLine(expr.ToString())
Next

' Print the result of the tree execution.
Console.WriteLine("The return value of the block expression:")
Console.WriteLine(result)

' This code example produces the following output:
'
' The result of executing the expression tree:
' Hello World!

' The expressions from the block expression:
' Write("Hello ")
' WriteLine("World!")
' 42

' The return value of the block expression:
' 42

Açıklamalar

Block yöntemleri bir BlockExpressionoluşturmak için kullanılabilir.

Özellikler

Yöntemler

Şunlara uygulanır