Global variable

I need to create a global variable and assign it a value in project one.
 
Then call the method from project 2 and use that variable.
 
I can instanitate the object and retreive the method in project 2.
  FulfilmentRequest fulfilmentRequest = new FulfilmentRequest();
 
       
            fulfilmentRequest.RetrieveByPIN(PIN);
 
But I need to set a variable in the RetrieveByPIN method and use that value in project 2, how can this be done?
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