通用扩展方法编译器错误

Question

我想编写一个编译器无法在运行时解析的通用扩展方法，虽然Visual Studio的intellisense确实找到它。

编译器错误是'SampleSolution.OtherGenericClass<SampleSolution.IGenericInterface<SampleSolution.ISimpleInterface>,SampleSolution.ISimpleInterface>' does not contain a definition for 'GenericExtensionMethod' and no extension method 'GenericExtensionMethod' accepting a first argument of type 'SampleSolution.OtherGenericClass<SampleSolution.IGenericInterface<SampleSolution.ISimpleInterface>,SampleSolution.ISimpleInterface>' could be found (are you missing a using directive or an assembly reference?)

这里是最简单的形式，一些示例代码，我可以拿出能重现问题。我知道我可以在IOtherGenericInterface中添加GenericExtensionMethod，但我需要扩展方法，因为它需要在IOtherGenericInterface实现之外。

public interface ISimpleInterface 
{ 

} 

public interface IGenericInterface<T> 
{ 

} 

public class GenericClass<T> : IGenericInterface<T> 
{ 

} 

public interface IOtherGenericInterface<TGenericDerived> 
{ 

} 

public class OtherGenericClass<TGenericInterface, TSimpleInterface> : 
    IOtherGenericInterface<TGenericInterface> 
    where TGenericInterface : IGenericInterface<TSimpleInterface> 
{ 

} 

public static class GenericExtensionMethods 
{ 
    public static IOtherGenericInterface<TGenericInterface> 
     GenericExtensionMethod<TGenericInterface, TSimple>(
      this IOtherGenericInterface<TGenericInterface> expect) 
     where TGenericInterface : IGenericInterface<TSimple> 
    { 
     return expect; 
    } 
} 

class Program 
{ 
    static void Main(string[] args) 
    { 
     var exp = new OtherGenericClass<IGenericInterface<ISimpleInterface>, 
             ISimpleInterface>(); 

     //exp.GenericExtensionMethod(); // This doesn't compile 
    } 
} 

Answer 1

它没有足够的信息来明确地解决了一般类型参数;你将不得不使用：

exp.GenericExtensionMethod<IGenericInterface<ISimpleInterface>, ISimpleInterface>(); 

特别要注意的是，where约束后分辨率验证- 他们不参与决议本身 - 这样的分辨率在所有它可以推断是TGenericInterface。