Printing field names of any wished class

Assume that we have some classes not having common interface or base class. How can we obtain names of the class wished? Is it possible? I’ve found the following code working as expected. However, I want to use it in a function by passing a class name. Is there any other way to achieve that?

 MemberInfo[] members = typeof(objectWhatever).GetMembers();
 foreach (MemberInfo memberInfo in members.Where(p => p.MemberType == MemberTypes.Property))
 {
      Console.WriteLine("Name: {0}", memberInfo.Name); // Name: MyField
 }

I tried to write the following, but not working syntactically.

 public static List<string> FieldNames(object obj ,string className)
 {
     dynamic changedObj = Convert.ChangeType(obj, Type.GetType(className));

     MemberInfo[] members = typeof(changedObj).GetMembers();

     foreach (MemberInfo memberInfo in members.Where(p => p.MemberType == MemberTypes.Property))
     {
         Console.WriteLine("Name: {0}", memberInfo.Name); // Name: MyField
     }
}