如何我找到具体的泛型重载使用反射？ [英] How to I find specific generic overload using reflection?

问题描述

我试图创建一个防爆pression 将调用特定的通用重载的方法（Enumerable.Average C>在我的第一个测试用例）。具体类型绑定不知道，直到运行时不过，所以我需要使用反射查找和创建正确的泛型方法（防爆pression 正在从分析的文本创建）。

I am attempting to create an Expression that will invoke a specific generic overloaded method (Enumerable.Average in my first test case). The specific type bindings are not known until runtime however so I need to use Reflection to find and create the correct generic method (the Expression is being created from parsed text).

所以，如果我知道在运行时，我想找到这个特定的过载：

So if I know at runtime that I want to find this specific overload:

public static double Average<TSource>(this IEnumerable<TSource> source, Func<TSource, int> selector)

我如何解决特定的MethodInfo 使用反射？

到目前为止，我有以下选择语句：

So far I have the following selection statement:

MethodInfo GetMethod(Type argType, Type returnType)
{
    var methods = from method in typeof(Enumerable).GetMethods(BindingFlags.Public | BindingFlags.Static)
      where method.Name == "Average" &&
      method.ContainsGenericParameters &&                              
      method.GetParameters().Length == 2 &&
      // and some condition where method.GetParameters()[1] is a Func that returns type argType
      method.ReturnType == returnType
      select method;

      Debug.Assert(methods.Count() == 1);
      return methods.FirstOrDefault();
}

以上范围缩小到三个重载，但我想反映，并找到具体的重载需要一个 Func键＆LT; TSource，INT＆GT; ，其中参数类型== typeof运算（INT）。

我难倒和任何帮助是AP preciated。

I am stumped and any help is appreciated.

推荐答案

<打击>您需要使用的 MethodInfo.MakeGenericMethod

编辑：好的，我误解了问题......这个方法应该做你想要的：

OK, I had misunderstood the problem... This method should do what you want :

MethodInfo GetMethod(Type argType, Type returnType)
{
    var enumerableType = typeof(IEnumerable<>).MakeGenericType(new Type[] { argType });
    Console.WriteLine(enumerableType);
    var methods = from method in typeof(Enumerable).GetMethods(BindingFlags.Public | BindingFlags.Static)
      let parameters = method.GetParameters()
      let genParams = method.GetGenericArguments()
      where method.Name == "Average" &&
      method.ContainsGenericParameters &&                              
      parameters.Length == 2 &&
      parameters[1].ParameterType.GetGenericTypeDefinition() == typeof(Func<,>) &&
      parameters[1].ParameterType.GetGenericArguments()[1] == argType &&
      method.ReturnType == returnType
      select method;

      return methods.FirstOrDefault();
}

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