How do I distinguish between generic and non generic signatures using GetMethod in .NET?

Assuming there exist a class X as described below, how do I get method information for the non-generic method? The code below will throw an exception.

using System;

class Program {
    static void Main(string[] args) {
        var mi = Type.GetType("X").GetMethod("Y"); // Ambiguous match found.
        Console.WriteLine(mi.ToString());
    }
}

class X {
    public void Y() {
        Console.WriteLine("I want this one");
    }
    public void Y<T>() {
        Console.WriteLine("Not this one");
    }
}

Answers


Don't use GetMethod, use GetMethods, then check IsGenericMethod.

using System;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var mi = Type.GetType("X").GetMethods().Where(method => method.Name == "Y"); 
        Console.WriteLine(mi.First().Name + " generic? " + mi.First().IsGenericMethod);
        Console.WriteLine(mi.Last().Name + " generic? " + mi.Last().IsGenericMethod);
    }
}

class X
{
    public void Y()
    {
        Console.WriteLine("I want this one");
    }
    public void Y<T>()
    {
        Console.WriteLine("Not this one");
    }
}

As a bonus - an extension method:

public static class TypeExtensions
{
    public static MethodInfo GetMethod(this Type type, string name, bool generic)
    {
        if (type == null)
        {
            throw new ArgumentNullException("type");
        }
        if (String.IsNullOrEmpty(name))
        {
            throw new ArgumentNullException("name");
        }
        return type.GetMethods()
            .FirstOrDefault(method => method.Name == name & method.IsGenericMethod == generic);
    }
}

Then just:

static void Main(string[] args)
{
    MethodInfo generic = Type.GetType("X").GetMethod("Y", true);
    MethodInfo nonGeneric = Type.GetType("X").GetMethod("Y", false);
}

Based on the answer of Konrad Morawski, I have created an enhanced extension method:

public static MethodInfo GetMethod (this Type i_oContainingType,
                                         string i_sMethodName,
                                         BindingFlags i_enBindingFlags,
                                         Type[] i_aoArgumentType,
                                         bool i_bGeneric)
{
  if (i_oContainingType == null)
    throw new ArgumentNullException (nameof (i_oContainingType));

  var aoMethod = i_oContainingType.GetMethods (i_enBindingFlags);
  var listoMethod = new List<MethodInfo> ();
  foreach (var oMethod in aoMethod)
  {
    if (!string.Equals (oMethod.Name, i_sMethodName))
      continue;
    if (oMethod.IsGenericMethod != i_bGeneric)
      continue;
    var aoParameter = oMethod.GetParameters ();
    if (aoParameter.Length != i_aoArgumentType?.Length)
      continue;
    int iParamMatch = 0;
    for (int ixParam = 0; ixParam < aoParameter.Length; ixParam++)
    {
      if (aoParameter[ixParam].ParameterType == i_aoArgumentType[ixParam])
        iParamMatch++;
    }
    if (iParamMatch != aoParameter.Length)
      continue;
    listoMethod.Add (oMethod);
  }
  if (listoMethod.Count != 1)
  {
    string sError = "Method with Name '" + i_sMethodName + "' and BindingFlags '" + i_enBindingFlags + "' and Parameter Types '" + i_aoArgumentType?.ToString ("', '") + "'";
    if (listoMethod.Count == 0)
      throw new MissingMethodException (sError + " has no match.");
    else
      throw new AmbiguousMatchException (sError + " has " + listoMethod.Count + " matches.");
  }
  return listoMethod[0];
}

public static MethodInfo GetPrivateInstanceMethod (this Type i_oContainingType,
                                                        string i_sMethodName,
                                                        Type[] i_aoArgumentType,
                                                        bool i_bGeneric)
{
  return GetMethod (i_oContainingType, i_sMethodName, BindingFlags.NonPublic | BindingFlags.Instance, i_aoArgumentType, i_bGeneric);
}

public static MethodInfo GetPublicInstanceMethod (this Type i_oContainingType,
                                                       string i_sMethodName,
                                                       Type[] i_aoArgumentType,
                                                       bool i_bGeneric)
{
  return GetMethod (i_oContainingType, i_sMethodName, BindingFlags.Public | BindingFlags.Instance, i_aoArgumentType, i_bGeneric);
}

Notice: i_aoArgumentType.ToString (..) is another extension method. I think you could guess what it does.


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