[RESOLVED] [02/03] Manipulate a form from a different class

[18experience]

Hello,
I have three classes, Common, A, and B. A and B reference Common so that they have access to variables inside it (I know this may be bad design, but I didn't do it, and I can't change it). From A, I can make a new B.Main form. No problem. However, we only want one copy of B.Main open at a time. So, we store a variable in Common called (basically) BMainOpen (boolean). In A, if they try to open a new instance of form B, and one is already open, I would like to give them the ability to jump to the point they wish, not just close it and open a new one. However, I need to know the...?... handle?... memory address?... of the open B.Main form, so I can manipulate it (load the correct data, set the selectedTabPage of the tab control, etc.). I thought I would just add another variable of type B.Main to Common, but I can't reference B from Common because B already references Common, which would cause circular dependency (the VB IDE won't let me).

In Form A
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim f as B.Main
If Not BMainOpen Then
f = new B.Main
Else
f.? = MyStoredVariable
End If
f.DoStuff()
f.Show()
End Sub

I just need to know what f.? and MyStoredVariable would be.

Confused? I tried to make it as simple as I could. Anyone know the solution?
Thanks

[RobDog888]

Use.ShowDialog() instead of .Show. That will stop the processing on form A so they cant go back until they close form B.

[18experience]

I regularly use ShowShowDialog, but, in this case, they want to be able to have Form B open and Form A still be responsive.

See, Form B is used to attach things (pics, pdfs, whatever) to different objects. So, it interacts heavily with things outside of our main program (not Form A, but the MDIParent of Form A).

[RobDog888]

Ok, then create a public object variable of form B in a Module. Then when you create the instance from A you can test for B being opened or created yet. If it is then just reuse it or messagebox to the user that they need to close the other form B first.

[18experience]

Well, that is what I tried to do. I tried to create a public object variable of class B form Main in my Common Class (we call them modules). But, B references Common, so Common can't reference B to get that Main form type.

So, I was thinking, maybe I could store the memory address of my open form B and then just DirectCast it something over in form A.

[RobDog888]

Im not sure of your form designs but if you created the form B object variable in a Module or in the general declarations section of your Main form then it should work.

"Common Class" is not a valid term. A Module is a Module and shouldnt be called anything else. It creates confusion as it just did for me.

[18experience]

I was trying to say, in the Common Module,

Dim frmOpenFormBMain as B.frmMain

But I couldn't reference it, because B referenced Common already. So, I just changed it to

Dim frmOPenFormBMain as Form

And, then, when I need to use it, I just DirectCast(frmOpenFormBMain, B.frmMain).

Problem solved.

Thanks for the help. Looking at this from different angles made me realize I could just use a generic form. Also, I tried it using and Object instead of a Form, and it worked like that, too.

[RobDog888]

You can also Inherit a form a different way, probably better too. In the forms designer code where it says "Inherits System.Windows.Forms.Form" you can change that to say "Inherits frmOpenFormBMain". Then it wont be dependant upon form b but it will only be "created" off of form b as a template.

This is called Visual Inheritance.