How to get a list of classes in a dll without the need for references? c# reflection [duplicate]

I want to get the list of classes in an assembly file like below:

Assembly a = Assembly.LoadFrom(dll);
classesList = a.GetTypes();

This assembly uses other references that I haven't them and during getting the classes that exist in them, this error happens:

Could not load file or assembly 'test.dll Version=1.0.7233.5369, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.

Actually I want to skip getting those classes that do not exist in the current assembly and just get its own classes. but GetTypes() method doesn't have any skip and it crashes.