gistfile1.cs

public static void RemoveDelegateFromEvent(object target, string EventPropertyName)
{
    var bindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance |BindingFlags.Static;

    var ev = target.GetType().GetEvent(EventPropertyName, bindingFlags);
    var f1 = target.GetType().GetField(EventPropertyName, bindingFlags);

    // search in base class
    if (f1 == null)
        f1 = target.GetType().BaseType.GetField(EventPropertyName, bindingFlags);

    if (f1 == null)
        throw new Exception("can't detach event handler");

    var del = f1.GetValue(target) as Delegate;

    if(del != null)
        ev.RemoveEventHandler(target, del);
}