Expression.Empty 方法

public:
 static System::Linq::Expressions::DefaultExpression ^ Empty();

public static System.Linq.Expressions.DefaultExpression Empty();

static member Empty : unit -> System.Linq.Expressions.DefaultExpression

Public Shared Function Empty () As DefaultExpression

傳回

DefaultExpression A 的性質等NodeType於 ，Default且Type性質設為 Void。

範例

以下程式碼範例展示了如何建立空運算式並將其加入區塊表達式。

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

// This statement creates an empty expression.
DefaultExpression emptyExpr = Expression.Empty();

// The empty expression can be used where an expression is expected, but no action is desired.
// For example, you can use the empty expression as the last expression in the block expression.
// In this case the block expression's return value is void.
var emptyBlock = Expression.Block(emptyExpr);

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

' This statement creates an empty expression.
Dim emptyExpr As DefaultExpression = Expression.Empty()

' An empty expression can be used where an expression is expected but no action is desired.
' For example, you can use an empty expression as the last expression in a block expression.
' In this case, the block expression's return value is void.
Dim emptyBlock = Expression.Block(emptyExpr)

備註

空表達式可用於預期表達式但不需動作的情況。 例如，你可以將空表達式作為區塊表達式的最後一個表達式。 此時區塊運算式的回傳值為 void。