How to refer two classes inside a single class in C#?

Question

I have three classes

1. MyBotDialog

2. DialogBot // this is generic class 

3. GeneralClass // this is where I want to refer MyBotDialog and DialogBot classes.

 

When I am declaring DialogBot and instance, it throws an error of generics

 

"The type or namespace T could not be found."

 

How to use Generic class in separate class?