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如何使用反射找到特定的通用重载?

linq-expressions .net-3.5 reflection generics c#

4

dkackman Srinivas Kokkula · 技术社区 · 16 年前

Expression Enumerable.Average Reflection 找到并创建正确的泛型方法(

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

MethodInfo

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();
}

Func<TSource, int> argType == typeof(int) .

4 回复 | 直到 16 年前

1

6

Thomas Levesque 16 年前

~~MethodInfo.MakeGenericMethod~~

编辑:好吧,我误解了这个问题。..此方法应该执行您想要的操作:

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();
}

2

1

tnyfst 16 年前

var call = Expression.Call(typeof(Enumerable),
             "Average",
            new Type[] { typeof(MyTSource) },
            enumerableParameter, lambdaParameter
                );

3

1

Pop Catalin 16 年前

static MethodInfo GetMethod(Type argType, Type returnType)
{
    var methods = from m in typeof(Enumerable).GetMethods(BindingFlags.Static | BindingFlags.Public)
                  where m.ContainsGenericParameters
                  && m.Name == "Average"
                  && m.GetParameters()[1].ParameterType.GetGenericTypeDefinition() == typeof(Func<,>)
                  && m.GetParameters()[1].ParameterType.GetGenericArguments()[1] == returnType
                  select m;
    return methods.First();
}

4

0

dkackman Srinivas Kokkula 16 年前

感谢@Joren的链接提示。这个例子根据论点计数进行区分,但它让我走上了正确的方向。

有效的选择是

var methods = from method in typeof(Enumerable).GetMethods(BindingFlags.Public | BindingFlags.Static)
where method.Name == Name &&
method.ContainsGenericParameters &&                                                    
method.ReturnType == returnType &&
method.GetParameters().Length == 2 &&
method.GetParameters()[1].ParameterType.GetGenericArguments().Count() == 2 &&
method.GetParameters()[1].ParameterType.GetGenericArguments()[1] == argType
select method;