当参数为通用参数时，Type.GetMethod的Type数组中应包含哪些Types? [英] What Types should be in the Type array for Type.GetMethod when a parameter is generic?

问题描述

如果我想通过反射调用泛型方法，则可以轻松使用

If I want to call a generic method through reflection, I can easily use this technique, unless:

1. 该方法只能通过其参数来区分.
2. 该方法的参数类型是该方法的类型参数之一.

调用Type.GetMethod(string, Type[])时如何在Type[]数组中指定通用参数?

How do I specify a generic parameter in the Type[] array when calling Type.GetMethod(string, Type[])?

示例:

public class Example
{
    //This is the one I want to call.
    public void DoSomething<T>(T t) { ... }

    public void DoSomething(Foo foo) { ... }

    public void CallDoSomething(Type type, object value)
    {
        MethodInfo method = typeof(Example)
        .GetMethod("DoSomething", new Type[] {/* what do i put here? */ });

        MethodInfo generic = method.MakeGenericMethod(type);
        generic.Invoke(this, value);
    }

推荐答案

当我必须找到

I'll give you the full "thing" I use when I have to find a Queryable.Select<TSource, TResult> Method (IQueryable<TSource>, Expression<Func<TSource, TResult>>) method... It is quite complex and checks nearly all:

MethodInfo selectMethod = (from x in typeof(Queryable).GetMethods(BindingFlags.Static | BindingFlags.Public)
                           where x.Name == "Select" && x.IsGenericMethod
                           let pars = x.GetParameters()
                           where pars.Length == 2
                           let args = x.GetGenericArguments()
                           where args.Length == 2 &&
                               pars[0].ParameterType == typeof(IQueryable<>).MakeGenericType(args[0]) &&
                               pars[1].ParameterType == typeof(Expression<>).MakeGenericType(typeof(Func<,>).MakeGenericType(args))
                           select x).Single();

您可以轻松地将其用作模板.

You can easily use it as a template.

请注意，未检查返回类型，因为返回类型没有重载.方法是static和public的事实由GetMethods()检查.我检查参数数量，通用参数数量，参数类型.然后，我使用Single()确保只有一种方法.这应该是面向未来的:即使Microsoft添加了另一个Queryable.Select方法，它也将是不同的".

Note that the return type isn't checked, because there is no overload for return types. The fact that the method is static and public is checked by the GetMethods(). I check number of parameters, number of generic arguments, type of parameters. Then I use the Single() to be sure that there is only one method. This should be future-proof: even if Microsoft added another Queryable.Select method, it would be "different".

在您的特定情况下:

MethodInfo method = (from x in typeof(Example).GetMethods(BindingFlags.Instance | BindingFlags.Public)
                     where x.Name == "DoSomething" && x.IsGenericMethod
                     let pars = x.GetParameters()
                     where pars.Length == 1
                     let args = x.GetGenericArguments()
                     where args.Length == 1 &&
                         pars[0].ParameterType == args[0]
                     select x).Single();

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