Question

我正在尝试编写一个编译器无法在运行时解析的通用扩展方法，尽管visual studio的intellisense确实找到了它。

编译器错误为'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?)

以下是我能想出的最简单形式的示例代码，可以重现问题。我知道我可以在GenericExtensionMethod中添加IOtherGenericInterface，但我需要一个扩展方法，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

没有足够的信息来明确地解析泛型类型参数;你将不得不使用：

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

特别要注意，{/ 1}}约束在解析后验证 - 它们本身不参与解析 - 所以在解析过程中它可以推断出where。

通用扩展方法的编译器错误

1 个答案: