using System;
using System.Reflection;

public interface ITest
{
    void TestFun(int arg);
}

public class TestClass : ITest
{
    void ITest.TestFun(int a)
    {
        Console.WriteLine("xxx");
    }
}

class Program
{
    public static void Main(string[] args)
    {
        InterfaceMapping interfaceMap = typeof(TestClass).GetInterfaceMap(typeof(ITest));
        MethodInfo methodInfo = interfaceMap.TargetMethods[0];
        MethodInfo methodInfo2 = interfaceMap.InterfaceMethods[0];
        Console.WriteLine(methodInfo.Name); // ITest.TestFun
        Console.WriteLine(methodInfo2.Name); // TestFun
    }
}