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

问题描述

更新：我已提交为在Microsoft Connect上的问题，如果你可以重现这个和/或希望看到这个固定的请帮助投票在那里的问题。

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我一直在试图解决这个问题几个小时。

真的会感谢你的想法/建议

首先，我有3个文件 Class.cs Definitions.cs 和 Program.cs 。我已在 http://pastie.org/1049492 上粘贴文件内容，以便您试用。 / p>

问题是，如果您在同一控制台应用程序项目中有所有3个文件。

但是，我有 Class.cs code> Definitions.cs 在一个库项目中，它是从主控制台应用程序项目引用的，只有 Program.cs 文件，编译失败：

• 委托 Act 不接受2个参数。


• 无法将lambda表达式转换为委托类型DC.Lib.Produce，因为块中的某些返回类型不能隐式转换为委托返回类型...

这里是一个包含3个项目的完整解决方案 - 1个将所有文件组合在一起，另一个将定义放在另一个项目中：

http://dl.dropbox.com/u/149124/DummyConsole.zip

我正在使用VS2010 RTW专业版。

解决方案

p>有趣。我认为您在C＃编译器中发现了一个实际的错误 - 虽然我可能会缺少一些微妙的东西。我写了一个略微简化的版本，避免了重载等的可能性，并且免除了额外的方法：

  // 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（输入，这个字符串应该出现。 
} 
} 
  

演示编译为一个程序集，

 > csc Test.cs Definitions.cs 
  

演示编译为两个错误的程序集：

 > csc / target：library Definitions.cs 
> csc Test.cs /r:Definitions.dll 
 
 Test.cs（5,43）：error CS1662：无法将lambda表达式
转换为委托类型'Produce< string>'
因为块中的一些返回类型不是
可隐式转换为委托返回类型
 Test.cs（5,52）：error CS1593：Delegate'Bar'不接受2个参数
  

我不能想到任何 ，一切都是公开的。除了 internal 的原因，该规范很少谈论程序集边界。

有趣的是，我得到相同的错误C＃3和4编译器。

电子邮件发送Eric和Mads现在...

可以使用显式参数列表解决这个问题。例如，在我的示例代码，这将工作：

 生产< string& produce = 
（Bar< string> next）=> input => next（输入，这个字符串应该出现。 
  

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.

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

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.

The problem is that, If you have ALL 3 files in the same console application project. The application compiles and runs just fine.

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:

• 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 ...

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

I'm using VS2010 RTW Professional edition.

解决方案

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.");
    }    
}

Demonstration of compiling as one assembly, with no errors:

> csc Test.cs Definitions.cs

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

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.

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

Emailing Eric and Mads now...

EDIT: 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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