Accessing a form from a thread running on a second form

have you tried passing the instance of Form1 to both Form2 and signal ?

It appears that every time I'm in the created thread and call something from form2 that it creates a new instance of the form. How do I reference the form that form1 created from the created thread?

The best approach to this would be to create an event in Class1 that gets raised whenever you want to indicate progress from your thread.

Then from your Form1 class you can handle the event and then set your label for form2

Note that you need to invoke back to the main thread in order to set the label for Form2.

I hope this helps, it is pseudo code but should hopefully explain what you need to do.

Hi,

I have a main form which starts up a thread as well as a 2nd form.

How do I make it so that I can access things such as labels on the 2nd form from the thread that was started on form1?

I have some sample code below...

Expand|Select|Wrap|Line Numbers

1. Public Class Form1
2.  
3.     Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
4.         Form2.Show()
5.         Form2.BringToFront()
6.         signal = New Class1
7.     End Sub
8.     Private signal As Class1
9.  
10. End Class
11.  
12.  
13. Public Class Class1
14.     Public Sub New()
15.         trd = New Threading.Thread(AddressOf task)
16.         trd.IsBackground = True
17.         trd.Start()
18.     End Sub
19.     Private trd As Threading.Thread
20.     Private Sub task()
21.         For i As Integer = 0 To 5
22.             Threading.Thread.Sleep(5000)
23.             Form2.Label1.Text = i.ToString
24.         Next
25.     End Sub
26. End Class
27.  

Any help would be much appreciated.

Thanks,

Wagz

If I pass Form2 to Class1 when I create it and create a delegate to handle the changing the text then it works.

I passed it in to Class1 in the constructor, is there a better way to do this? In the future I'd like to be able to possibly add additional forms and therefore don't necessarily want to have to have to modify the class every time I create a new form.

Below is the code I used:

jjvainav, I couldn't get your method to work.

I raised the event in Class1 and handled it in Form1, but when I go to change the text in Form2 it creates a new instance of Form2.

Try this:

jjvainav, I couldn't get your method to work.

I raised the event in Class1 and handled it in Form1, but when I go to change the text in Form2 it creates a new instance of Form2.

Expand|Select|Wrap|Line Numbers

1. Public Class Form1
2.     Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
3.         Form2.Show()
4.         Form2.BringToFront()
5.         signal = New Class1()
6.     End Sub
7.     Private WithEvents signal As Class1
8.     Public Sub SetForm2Text(ByVal text As String) Handles signal.SetText
9.         Form2.Label1.Text = text
10.     End Sub
11. End Class
12.  
13. Public Class Class1
14.     Public Sub New()
15.         trd = New Threading.Thread(AddressOf task)
16.         trd.IsBackground = True
17.         trd.Start()
18.     End Sub
19.     Public Event SetText(ByVal text As String)
20.     Private trd As Threading.Thread
21.     Private Sub task()
22.         For i As Integer = 0 To 5
23.             Threading.Thread.Sleep(5000)
24.             RaiseEvent SetText(i.ToString)
25.         Next
26.     End Sub
27. End Class

All forms that you create inheri the base class Form.

If you can identify which forms will be sent (like you send Form1) to Class1
Also identify the methods that these forms will have in common,

Put them all into an interface, and pass the instance of the Form as the interface type you just created.

This way, you will only need to pull the interface type, and call the method, which will do the trick for you