Windowsform and uercontrol, implementing changes to them.

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5.00/5 (1 vote)

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Hi,

I'm programming a windows form application, I'm having a problem in implementing a code to my user controls,

let's say, all my forms inherit from my base class and in my base class I have the code below,

VB

Public Class BaseForm
    Inherits System.Windows.Forms.Form

    Protected Overrides Sub OnVisibleChanged(e As System.EventArgs)
        MyBase.OnVisibleChanged(e)

        If Me.Visible Then ' create Handler to each Button when Form is shown (becomes visible)
            For Each myControl As Control In Me.Controls
                If myControl.GetType Is GetType(Button) Then
                    AddHandler myControl.Click, AddressOf TestModul.ClickHandler
                End If
            Next
        Else ' remove Handler from each Button when Form is left (becomes unvisible)
            For Each myControl As Control In Me.Controls
                If myControl.GetType Is GetType(Button) Then
                    RemoveHandler myControl.Click, AddressOf TestModul.ClickHandler
                End If
            Next
        End If

    End Sub
End Class

The test module is as follows:

VB

Module TestModul
    Public Sub ClickHandler(sender As Object, e As System.EventArgs)

        Dim mySender As Control = sender
        MessageBox.Show(mySender.Name + vbCrLf + mySender.Parent.Name)
        If (mySender.Parent.GetType().ToString().Contains("UserControl")) Then
            MessageBox.Show("Its a user control")
        End If

    End Sub
End Module

So far everything is working properly, but the problem is with implementing the code to my usercontrols which all inherit from my baseusercontrol which is written below:

VB

Public Class BaseUserControl
    Inherits System.Windows.Forms.UserControl

   Protected Overrides Sub OnVisibleChanged(e As System.EventArgs)
        MyBase.OnVisibleChanged(e)

        If Me.Visible Then ' create Handler to each Button when Form is shown (becomes visible)
            For Each myControl As Control In Me.Controls
                If myControl.GetType Is GetType(Button) Then
                    AddHandler myControl.Click, AddressOf TestModul.ClickHandler
                End If
            Next
        Else ' remove Handler from each Button when Form is left (becomes unvisible)
            For Each myControl As Control In Me.Controls
                If myControl.GetType Is GetType(Button) Then
                    RemoveHandler myControl.Click, AddressOf TestModul.ClickHandler
                End If
            Next
        End If

    End Sub

End Class

this procedure must do as follows, anytime a button is pressed it must show me a messagebox and display the name of that button and the form which contains the button.

What I have tried:

as is traced it it does not enter this condition,

VB

If myControl.GetType Is GetType(Button) Then

and see's it as a false condition. I removed the If statement and saw that again it doesn't read the line of code

VB

AddHandler myControl.Click, AddressOf TestModul.ClickHandler

so again the change will not be done on the buttons.

Well in on of my forms it's working, because I opened it and manually removed the line of inheritence after the name of those classes, I just removed the line ' Inherits baseusercontrol' and rewrote it. then it worked.

But I shouldn't do this for all other classes. What would be the automated way to that?

In advance thank you for your help.

Posted 16-Jul-16 0:16am

m.r.m.40

Updated 16-Jul-16 10:03am

v2

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Comments

m.r.m.40 16-Jul-16 6:16am

The codes above are given to me by a professional member 'Ralf Meier'.

Richard MacCutchan 16-Jul-16 7:01am

Then you should ask Ralf Meier for help.

m.r.m.40 16-Jul-16 7:04am

I don't know how to contact him.
I just found out what the problem is. I'll just post it here.

Richard MacCutchan 16-Jul-16 7:28am

Go back to the message where he gave you this code.

Ralf Meier 16-Jul-16 15:56pm

I would not add this code to the usercontrol. I would do it in the Form as described. When you iterate through the Forms.control-collection you could also check if each of those controls have also child-controls in it - in this case you check the child-controls and connect them (if necessary) also to the handler. See my solution (2) to this ...

[no name] 16-Jul-16 7:48am

Your UserControl is probably not the Container for the button.

Verify:
a.) Move your Control in Designer, I assume the button remains on same Location.
b.) Derive for a test instead from UserControl but from Panel

BillWoodruff 16-Jul-16 8:01am

Check to see if the Buttons in the UserControl are on the "surface" of the UserControl (contained in the UserControl's ControlCollection). If some, or all, of the Buttons are inside other ContainerControls, you will not access them through Me.Controls ... instead use Me.Controls.Find with the recursive option set to 'true.

Philippe Mori 18-Jul-16 9:57am

Why would you add/remove handler according to visibility? How would you click on an invisible button?

m.r.m.40 19-Jul-16 4:47am

I think you missed this line of comment,
' remove Handler from each Button when Form is left (becomes unvisible)

Philippe Mori 19-Jul-16 8:50am

And you haven't respond to the question... It look like you copied someone else poor code!

Thus I will ask my question differently. Tell me what does happen if you remove all the code inside OnVisibleChanged.

Ralf Meier 19-Jul-16 14:54pm

The code-suggestion comes from me ...
I selected the OnVisibleChanged-method for adding and removing of the handlers because this method is directly to the Form.show and/or Form.hide-command. In my opinion I remove unneeded connections. Of cause it is also possible to connect the handlers with Form.OnHandleCreated and to remove it by Form.OnHandleDestroyed. There are severall possibilities - I choosed this one.

Anyway - you are right with the Visibility. This will only come from the Form. No control on the Form or any ContainerControl of the Form becomes invisible if the Form hides.

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User 11060979 · Answer 1 · 2016-07-16T02:07:00

To let act your Control as a Container you Need to derive from ContainerControl. In your case the form is the Container for the button you placed on your control.

For tests it is very convinient to derive from Panel. This because you can show e.g. a border.

[Edit]
Finally: The harder (but probably correct) way is described here on CP Designing Nested Controls[^]

Hope it helps.

[Edit1] The OnVisible Story
Note: I would suggest to avoid adding and removing event handlers frequently like you do it in your code. Instead you should try with checking parent.Visible in your event handler.

Here an idea how you can solve the "OnVisible" request as a Default behaviour of your control. I did it in c# (I don't know VB) but I'm sure it is no Problem for you to convert it to VB.

C#

 public partial class MyPanel : Panel // ContainerControl //UserControl
 {
     Form lastParent= null;

     // Install Event handler to the control
     protected override void OnParentChanged(EventArgs e)
     {
         // Call base class
         base.OnParentChanged(e);

         // Remove handler from previous hosting form
         if (lastParent != null)
         {
             lastParent.VisibleChanged -= ParentVisibleChanged;
             lastParent = null;
         }

         // Find the new hosting form. Most probably the same, but who knows
         Control parent = this.Parent;
         while (parent != null)
         {
             if (parent is Form)
             {
                 lastParent = (Form)parent;
                 lastParent.VisibleChanged += ParentVisibleChanged;
                 break;
             }
             parent = parent.Parent;
         }
     }

     protected void ParentVisibleChanged(object sender, EventArgs e)
     {
         // Debug only
         MessageBox.Show("ParentVisibleChanged");

         // Do what you need to do for form visible change
         // Should always be true.
         if (lastParent != null)
         {
             if (lastParent.Visible)
             {
             }
             else
             {
             }
         }
     }
  ...
  .....
}

Ralf Meier · Answer 2 · 2016-07-16T10:03:00

Solution 2

I would change the posted methods like this :

VB

Protected Overrides Sub OnVisibleChanged(e As System.EventArgs)
        MyBase.OnVisibleChanged(e)

        CheckControlCollection(Me , Me.Visible)

End Sub

VB

Private Sub CheckControlCollection(myHost As Control , state as boolean)
        For Each myControl As Control In myHost.Controls
            If myControl.GetType Is GetType(Button) Then
                if state then AddHandler myControl.Click, AddressOf TestModul.ClickHandler
                if not state then RemoveHandler myControl.Click, AddressOf TestModul.ClickHandler
            End If

            If myControl.Controls.Count > 0 Then
                CheckControlCollection(myControl , state) ' <- I have modified this line because of a mistake in it ...
            End If
        Next
End Sub

But please note - this code is not tested ...
Both methods still belong to your baseform. You don't need to integrate it to the usercontrol or any other containercontrol.
Your code in your usercontrol doesn't work because the usercontrol doesn't change it's Visible-State. If you want to do it in the usercontrol in the same way you should override annother method - but I prefer THIS way ...

Additional :
If you have further question (to this code or something else) you only need to comment this answer / solution or you should comment one of my comments. In both cases I get a message and if I'm online again I answer - if possible ... ;-)

Additional (2) :
>> I modified the code because of a mistake in it ...

Additional (3) - modified ClickHandler :

VB

Public Sub ClickHandler(sender As Object, e As System.EventArgs)

    Dim mySender As Control = sender
    Dim myChildPath As String = mySender.Name

    Do
        If mySender.Parent Is Nothing Then Exit Do
          mySender = mySender.Parent
        myChildPath += vbCrLf + mySender.Name
    Loop

    MessageBox.Show(myChildPath)

End Sub

Posted 16-Jul-16 10:03am

Ralf Meier

Updated 19-Jul-16 8:40am

v7

Comments

m.r.m.40 18-Jul-16 2:10am

Thank you, but no, it's not working on usercontrols.

Ralf Meier 18-Jul-16 3:36am

I think, you understood me wrong. This code is not designed to work on usercontrols - it should work also on the (base-)form. It replaces the code-samples I gave to you in the other question ...

Do you really want to have a code like this working on usercontrols ?

m.r.m.40 18-Jul-16 3:51am

Yes, this new code and the previous one both work as well,
the problem I have now is how to have this module working on my usercontrols.

Ralf Meier 18-Jul-16 6:47am

I'm sorry - I could not follow you. Where do you have the Problem ?
You don't have anything to change on your UserControls. Every UserControl is placed on a Form which derives from your BaseForm which has the code and can detect the Button on the Baseform as well as it could detect it on a UserControl on the Baseform as well as it could detect it on a Control in a Control in a Control on the Baseform.

Please give me an example for your issue ...

m.r.m.40 19-Jul-16 1:09am

Something came into my mind,

These lines of code:

If Me.Visible Then
CheckControlCollection(Me, Me.Visible)
Else
CheckControlCollection(Me, Me.Visible)
End If

do not need 'if' and 'else' statement. the single line
CheckControlCollection(Me, Me.Visible)
will work as well.

Ralf Meier 19-Jul-16 2:33am

Yes ... you are right - I have never seen this - sorry.
But what about your problem ? Are you a step further ? Or how could I help you ...?

m.r.m.40 19-Jul-16 3:16am

I'm still working on it,
It's a form inherited from base form named 'MainForm', Inside it there's a panel named 'Panel1', the usercontrols open inside the panel. and the code which you gave me does not work on this form and the usercontrols which open inside it, However that work properly of the forms of an other project as a test prject.

Ralf Meier 22-Jul-16 3:34am

Hi,
tell me something about your state ...
Did you see my last changes (3 days ago) to the code ?

m.r.m.40 23-Jul-16 2:02am

Hi,
Yes I saw it, thanks.
First I must thank you for helping me and spending time for this problem, unfortunately it was our weekend, I start working on it from today till the next five days, I'll Update the state's by replying your comments,
Thanks a lot.

Ralf Meier 23-Jul-16 6:59am

no matter ... if I really could help you ...

m.r.m.40 23-Jul-16 3:23am

I'm thinking about overriding the onload function of the system.windows.forms.form, and inside it, put the code above which you gave me. so each time a form loads, it will add the handler to the buttons inside it. you agree with it?

Ralf Meier 23-Jul-16 6:58am

Perhaps ...
If you look at the Form-class you find a lot of Event-Methods which belong to it.
For Example :
OnHandleCreated - OnHandleDestroyed : when the Form-Instance is builded / disposed
OnVisibleChanged (as I described) comes with Form.Show and Form.Hide
Perhaps also OnActivated - OnDeActivated

You should look which method matches best to what you want to do.
As I described : normally I remove Eventhandlers when they are no more necessary. If you Hide your Form they aren't necessary any more - so I would remove them. But it is also no mistake if you keep them alive because, if the Form is hided, it could not raise any Event. But you should know : every Handler which is manually created by you MUST manually removed by you. If you forget this it could have "interesting" effects - perhaps the Garbage-Collector doesn't free the Memory and parts of the function are still active ...

m.r.m.40 25-Jul-16 6:19am

Hi Ralf,

I fixed it using the function below

Protected Overrides Sub InitLayout()

inside this function I put the first code that you gave me, and it fixed my problem. do you think I should post it as an answer?
Finaly now that the problem is solved, do you think I should link all my questions that are asked about the same context by putting a comment under each of them?

Thank you for all the support that you gave me.

Ralf Meier 25-Jul-16 6:50am

Of course ... you could. But please remember : one of the first advices I gave to you was : "If you want to use it in an UserControl you should override different Event-Methods".

But ... becasuse of the great number of comments an tries to answer : what is your final goal ? Is it only for testing and/or learning how it works ... or is there another reason ?

m.r.m.40 25-Jul-16 15:31pm

Of course I'm learning and beside it I'm solving some problem which I've already been stuck in. However you can read my last 5 question that are asked in the same context.

Thank you for helping me.

BillWoodruff 23-Jul-16 23:01pm

+5

Ralf Meier 25-Jul-16 3:33am

Thank you, Bill ... :)