.Net class library and windows application projects

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Fuma

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I have a windows application project which has a form (frmGUI) with a label control (Label1) and a button. When i click the button, it will call the doStuff's doLoop function and display the i value in frmGUI.Label1.Text (the line in bold). Is that possible

Code: 
Imports Test

Public Class frmGUI

    Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click
        [COLOR="Green"]'call the testStuff.doLoop("value")[/COLOR]

    End Sub

End Class

I also have a class library project called Test with the following class:

Code: 
Public Class doStuff

  Public Function doLoop(ByVal db As String)
  
    For i = 0 To 10  
      [B]frmGUI.Label1.Text = i[/B]
    Next i
    
    Return Nothing
  End Function

End Class

Edit: I can't seem to indent my quotes.
 
Last edited:
add Application.DoEvents() before the line "Next i" to give GIU time to update.
 
Ahhh.. my eyes! VB!! Ahhh!

OK.. now for some useful info - post your question on StackOverflow.com.

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Put you code in [ code ] [ /code] blocks to see your indents.

You can do what you want, but it's not ideal. What you need to do is pass the instance of the form through to the class library. Either via the constructor OR in the method you are calling. I don't like this method of doing things except in the case of dialog boxes, but that's a different argument.

Try this:
Code: 
Imports Test
Public Class frmGUI
    Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click
        testStuff.doLoop("value", Me)
    End Sub
End Class

Imports System.Windows.Forms
Imports System.Threading
Imports Namespace.Where.frmGUI.Is.Declared
Public Class doStuff
    Public Function doLoop(ByVal db As String, ByVal formToUpdate AS frmGUI)
        For i = 0 To 10 
            formToUpdate.Label1.Text = i.ToString
            Thread.Sleep(500) 'Give it time to update otherwise you'll only see the last value
        Next i
        Return Nothing
    End Function
End Class

EDIT: You should rather have you class library return a value and then update the form in it's own class.

Something like:
Code: 
Me.Label1.Text = testStuff.doLoop("value")
 
The frmGUI is in the prjFrontEnd project.
I had to create an exe for prjFrontEnd and added it as a reference, and by default a class library doesn't have System.Windows.Forms by default. So I had to add it as well.
I tried:
Code: 
Imports prjFrontEnd  
Imports System.Windows.Forms

Public Class doStuff

  Public Function doLoop(ByVal db As String)
    dim frmGUILabel as frmGUI = new frmGUI
    For i = 0 To 10 
      frmGUILabel.[B]Label1.Text [/B]= i
      Application.DoEvents()
    Next i

  Return Nothing
End Function

End Class

It doesn't seem to find Label1
 
Last edited:
Heita_Hola said:
The frmGUI is in the prjFrontEnd project.
I had to create an exe for prjFrontEnd and added it as a reference, and by default a class library doesn't have System.Windows.Forms by default. So I had to add it as well.
Click to expand...
That's normal...
Heita_Hola said:
It doesn't seem to find Label1
Click to expand...

You need to make it Public. In the form designer check the properties in the Label1. In the property panel Design->Modifiers.

Dimming a new form will not help you as you want to update the existing form? That's why you need to pass it as a parameter...
 
dequadin said:
That's normal...


You need to make it Public. In the form designer check the properties in the Label1. In the property panel Design->Modifiers.
Click to expand...
Thank you. I'm such a noob.

Dimming a new form will not help you as you want to update the existing form? That's why you need to pass it as a parameter...
Click to expand...

When I call testStuff.doLoop("value", Me), it says "Value of type 'prjFrontEnd.frmGUI' cannot be converted to 'prjFrontEnd.frmGUI'
 
Heita_Hola said:
When I call testStuff.doLoop("value", Me), it says "Value of type 'prjFrontEnd.frmGUI' cannot be converted to 'prjFrontEnd.frmGUI'
Click to expand...

That's weird, this complies fine for me:
Code: 
Public Class Class1
    Public Sub DoIt(ByVal Form As mainForm)
    End Sub
End Class

Public Partial Class mainForm
    Inherits Form
 
    Public Sub New()
        InitializeComponent()

        Dim c1 As New Class1()
        c1.DoIt(Me)
    End Sub
End Class

EDIT: It seems you are having some sort of referencing issue. Are you using project references or file references? Check out this thread
 
Last edited:
I tried using both project and file references, and still.
 
Last edited:
Hmmm, what dequadin suggested should work fine.

What i suggest you do is create a new project file and run his code in there, check how it works, and then try and apply it to your own project.

That's what I usually do, and it's easier to see where you can go wrong. The error message you get basically means that you're doLoop function is expecting something and you're sending it something else, so the "cast" fails.
 
Heita_Hola said:
I tried using both project and file references, and still.
Click to expand...

I just realised something here. You have two separate projects? One Class Library project and one Windows Forms project?

If that's the case you cannot do this. Because you need to reference the WinForms project from the Class library (to pass the form instance) and you need to reference the Class library from the WinForms project (to call the method). This is not allowed, two projects cannot reference eachother.

Can't you add the class to your WinForms project and then use it there (this will work fine).
 
dequadin said:
I just realised something here. You have two separate projects? One Class Library project and one Windows Forms project?

If that's the case you cannot do this. Because you need to reference the WinForms project from the Class library (to pass the form instance) and you need to reference the Class library from the WinForms project (to call the method). This is not allowed, two projects cannot reference eachother.

Can't you add the class to your WinForms project and then use it there (this will work fine).
Click to expand...

I wish I could add the class to my WinForms project, but we grouped everything accordingly. Some of the projects have a solution that has about 5 different class library projects grouped according to what they do (xml, db, emails, console, http stuff). So I can't just move that class.

So basically I have a label in one of the forms that must display what the doLoop (as per example) is busy with, coz at the moment, the form just stays there looking like nothing is happaning whereas that doLoop is processing like 500 records per i (there are about 1000 i's). Unless I can use another method to to display what the current i is. Any ideas?
 
Heita_Hola said:
I wish I could add the class to my WinForms project, but we grouped everything accordingly. Some of the projects have a solution that has about 5 different class library projects grouped according to what they do (xml, db, emails, console, http stuff). So I can't just move that class.

So basically I have a label in one of the forms that must display what the doLoop (as per example) is busy with, coz at the moment, the form just stays there looking like nothing is happaning whereas that doLoop is processing like 500 records per i (there are about 1000 i's). Unless I can use another method to to display what the current i is. Any ideas?
Click to expand...

Okay, my suggestion is to then have your class library expose an event. Then I would subscribe to this event from the form you need to update. You can then raise this event every iteration (or maybe every 5 iterations of it's processing really quickly) of your loop, and update the form that way.

This is how BackgroundWorker handles this scenario, with the ProgressChanged Event.
 
Try what dequadin said earlier. Let the doLoop return a value (i or whatever) and show it within the WinForms project.
 
Have you tried passing the Label through to the doLoop method by reference and update it like that? That way you can still have them in different projects, with only the WinForms project referencing the Class Library project... You will only need to include the System.Windows.Forms namespace to your Class Library...
 
FarligOpptreden said:
Have you tried passing the Label through to the doLoop method by reference and update it like that? That way you can still have them in different projects, with only the WinForms project referencing the Class Library project... You will only need to include the System.Windows.Forms namespace to your Class Library...
Click to expand...

+1 OMG such a simple solution :)

Label is a reference type so you can still update the .Text property without having to pass it by reference, so I wouldn't do that.
 
dequadin said:
Okay, my suggestion is to then have your class library expose an event. Then I would subscribe to this event from the form you need to update. You can then raise this event every iteration (or maybe every 5 iterations of it's processing really quickly) of your loop, and update the form that way.

This is how BackgroundWorker handles this scenario, with the ProgressChanged Event.
Click to expand...

You are talking jargon now. LOL. I'm a noob.
By example is way better.
 
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