Lamba表达式无法按预期使用 [英] Lamba expression cannot be used as expected

问题描述

下面的代码产生编译器错误期望表达"(带下划线的子句).

The following code produces the compiler error "Expression expected" (Sub is underlined).

Dim lambda As Action(Of Integer) = Sub(x) Console.WriteLine(x)

为什么这不起作用?

注意:相应的C#代码有效:

Note: The corresponding C# code works:

Action<int> lambda = x => Console.WriteLine(x);

推荐答案

我猜您正在使用Visual Studio2008.VB.NET中的操作lambda((Sub关键字)

I guess you're using Visual Studio 2008. Action lambdas in VB.NET (Sub keyword) have been added in VB 10, which ships with Visual Studio 2010. The same is true for multi-line lambdas, by the way.

请注意，这不是框架问题，而是编译器问题:只要使用VS 2010编译器，即使在.NET 3.5项目中也可以使用动作lambda.

Note that this is not a framework issue, but a compiler issue: You can use action lambdas even in .NET 3.5 projects, as long as you use the VS 2010 compiler.

C#在VB之前有动作lambda，这就是为什么C#示例即使在VS 2008中也可以工作的原因.

C# had action lambdas before VB, which is why the C# example works even in VS 2008.

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