Deriving class names from DLL file.

Is there any code that we can write in Visual Studio and get the class names of particular dll file? I am very new to coding and need aasistance.

I got below code from web but I do not know how to add Assembly ref to the code.
//Read the dll.
Assembly assembly = Assembly.LoadFrom(@"E:\test.dll");

//Get the list of class name .
Type[] types = assembly.GetTypes();

List<string> classname = new List<string>();
foreach (Type t in types)
{
classname.Add(t.Name);
}