如果委托定义放在另一个项目编译失败？ [英] Compilation fails if delegate definitions is put in another project?

问题描述

更新：我提起这个作为的微软连接如果你能重现此和/或希望能看到这个固定请帮忙投票了问题那边。

UPDATE: I've filed this as an issue on Microsoft Connect if you can reproduce this and/or would love to see this fixed please help vote up the issue over there.

我一直想现在就解决这个问题了几个小时。结果
会很感激的任何想法/建议你能想到的

I've been trying to solve this problem for hours now.
Would really appreciate whatever idea/advice you can think of.

首先，我有3个文件 Class.cs Definitions.cs 和的Program.cs 。我在上 http://pastie.org/1049492 粘贴文件内容为你尝试。

First of all, I have 3 files Class.cs Definitions.cs and Program.cs. I've pasted file contents over at http://pastie.org/1049492 for you to try out.

的问题是，如果你在同一个控制台应用程序项目的所有3个文件。该应用程序编译和运行就好了。

但是，如果我有 Class.cs 和 Definitions.cs 中，由具有主控制台应用程序项目引用到库的项目只有的Program.cs 文件，编译失败：

If however, I have Class.cs and Definitions.cs in a "library" project which is referenced to from the main console application project which has only the Program.cs file, compilation fails with:

• 代表法用不了2个参数。


• 无法转换lambda表达式的委托类型'DC.Lib.Produce'，因为一些块的返回类型不隐式转换为委托返回类型...

• Delegate Act does not take 2 arguments.
• Cannot convert lambda expression to delegate type 'DC.Lib.Produce' because some of the return types in the block are not implicitly convertible to the delegate return type ...

下面是3个项目的完整解决方案 - 1与放在其他项目的定义结合在一起，另外所有文件：结​​果
http://dl.dropbox.com/u/149124/DummyConsole.zip

Here is a complete solution with 3 projects -- 1 with all files combined together and another with the definitions put in another project:
http://dl.dropbox.com/u/149124/DummyConsole.zip

我使用VS2010 RTW专业版。

I'm using VS2010 RTW Professional edition.

推荐答案

有意思。我的认为的你已经发现，在C＃编译器实际的错误 - 尽管我可能会丢失一些微妙。我写了一个略微简化版本，它避免了超载等开始发挥作用的可能性，以及与额外的方法免除：

Interesting. I think you've found an actual bug in the C# compiler - although I may be missing something subtle. I've written a slightly simplified version which avoids possibilities of overloading etc coming into play, and which dispenses with the extra method:

// Definitions.cs
public interface IData { }
public delegate IData Foo(IData input);
public delegate IData Bar<T>(IData input, T extraInfo);
public delegate Foo Produce<T>(Bar<T> next);

// Test.cs
class Test
{
    static void Main()
    {
        Produce<string> produce = 
            next => input => next(input, "This string should appear.");
    }    
}

示范：

Demonstration of compiling as one assembly, with no errors:

> csc Test.cs Definitions.cs

编译两个组件有错误示范：

Demonstration of compiling as two assemblies with errors:

> csc /target:library Definitions.cs
> csc Test.cs /r:Definitions.dll

Test.cs(5,43): error CS1662: Cannot convert lambda expression 
        to delegate type 'Produce<string>'
        because some of the return types in the block are not 
        implicitly convertible to the delegate return type
Test.cs(5,52): error CS1593: Delegate 'Bar' does not take 2 arguments

我想不出的任何的原因，这应该是在不同的组件不同，因为一切都公开。该规范比其它组件边界很少说话了内部的原因。

I can't think of any reason why this should be different across different assemblies, as everything's public. The spec rarely talks about assembly boundaries other than for internal reasons.

有趣的是，我得到两个同样的错误。在C＃3和4的编译器

Interestingly, I get the same error for both the C# 3 and 4 compilers.

通过电子邮件发送Eric和现在的Mads ...

Emailing Eric and Mads now...

编辑：请注意，可以解决此使用一个明确的参数列表。例如，在我的示例代码，这将工作：

Note that you can work around this using an explicit parameter list. For example, in my sample code, this will work:

Produce<string> produce =
    (Bar<string> next) => input => next(input, "This string should appear.");

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