how to wire 2 User Controls together with ID

Question

I have a CaseForm with these controls placed in it. UserControl1 is above UserControl2.

TabControl1 has UserControl1

TabControl2 has UserControl2

 

UserControl1-upon btnSave(), it generates a new case number and a new caseID. Which saves to db. This works fine.

The caseID is the key ID for both. UserControl2 case is part of the UserControl1 case. 

 

A case has to be created in UserControl1, in order to create a new subcase in UserControl2. It needs to pass the caseID to it.

Now I get null object error in my Save() here:

CaseRecord.SubCase.CaseID = CaseRecord.CaseID.Value; 

 How do I pass the caseID from UserControl1 to UserControl2 to save. 

 

Thank you for any help!