Is there a way to tell if a method is an event or property accessor?

Question

That is, how can I, given a MethodInfo check if a method is the getter or setter of a property or the adder or remover or firer (?) of an event, without enumerating all the Property/EventInfos in the containing type. Does the compiler mark these methods with some information that would allow me to know when my MethodInfo is one?

Answer 1

At least one difference between a manually declared method and one that was generated by the compiler is the presence of a SpecialName attribute in its MethodInfo object:

To find out which property the method is linked to you would inspect PropertyInfo objects to find their corresponding GetMethod and SetMethod properties, which would link to those methods.

Example LINQPad program:

void Main()
{
    typeof(Test).GetProperties().Select(property => new { property.MetadataToken, property.Name, getter = property.GetMethod?.MetadataToken, setter = property.SetMethod?.MetadataToken }).Dump();
    typeof(Test).GetMethods().Select(method => new { method.MetadataToken, method.Name, IsSpecial = (method.Attributes & MethodAttributes.SpecialName) != 0 }).Dump();
}

public class Test
{
    public int Value
    {
        get;
        set;
    }
}

Output:

Answer 2

MethodInfo.IsSpecialName is set to true for properties and events accessors, also for some other special methods as operators overload and etc. So you can check this flag along with checking the parameter type. The following test program will output the event add/remove accessors:

public class MyEventClass {
private event EventHandler test;
public event EventHandler TestEven {
  add { test += value; }
  remove { test -= value; }
}

}

class Program { static void Main(string[] args) {

  Type myTestClassType = typeof (MyEventClass);
  var methods = myTestClassType.GetMethods();
  foreach (var methodInfo in methods)
  {
    if (methodInfo.IsSpecialName)
    {
      var parameters = methodInfo.GetParameters();
      if (parameters.Count() == 1 && parameters.ElementAt(0).ParameterType == typeof (EventHandler) &&
          (methodInfo.Name.Contains("add") || methodInfo.Name.Contains("remove")))
      {
        Console.WriteLine(methodInfo.Name);
      }

    }
  }

}

}