[Resolved] Making ALL comboboxes on a form ReadOnly

[Monkz]

Is there a simple way to make all comboboxes on a form to be readonly upon form load?

Rather than doing:

ComboBox1.ReadOnly = True
Combobox2.ReadOnly = True

And so on...

[ForumAccount]

ComboBoxes don't have a ReadOnly property. But in general the answer to your question is that you loop through all the controls on the form and test if it's a combobox, if it is then you do whatever you want with it:

For Each ctl As Control In Me.Controls
     If TypeOf ctl Is ComboBox Then
          'Do something with the combobox
     End If
Next
'Or with LINQ
Dim cbxes = (From ctl In Me.Controls _
             Where TypeOf ctl Is ComboBox _
             Select ctl).OfType(Of ComboBox)()

Note that this code doesn't check nested controls.

[Monkz]

Woops i meant textbox.. i dont know what i was thinking and thanks! thats what i needed!

[Monkz]

But what do i use in front of:

.ReadOnly = True

when i use that format?

[ForumAccount]

Assuming you are using the For Next loop:

For Each ctl As Control In Me.Controls
     If TypeOf ctl Is TextBox Then
          DirectCast(ctl, TextBox).ReadOnly = True
     End If
Next

[Hack]

I like to toggle things in case I want to do the opposite sometimes. Since you seem to have a reason not to set this in design, it stands to reason you might want to change your mind.

Public Class Form1
    Private Sub MakeTBReadOnly(ByVal IsReadOnly As Boolean)
        Dim ctrl As Control = Me.GetNextControl(Me, True)
        Do
            If TypeOf ctrl Is TextBox Then
                CType(ctrl, TextBox).ReadOnly = IsReadOnly
            End If
            ctrl = Me.GetNextControl(ctrl, True)
        Loop Until ctrl Is Nothing
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        MakeTBReadOnly(True)  'make them readonly
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        MakeTBReadOnly(False)  'make them read/write
    End Sub
End Class

[NickThissen]

I would just like to add that the For loop ForumAccount uses will not visit nested controls (controls in a panel/groupbox/tabpage, whatever), as he mentioned already, whereas the Do loop used by Hack does.

Also, to both of you, isn't it better to use the following:

Dim tb As TextBox = TryCast(ctrl, TextBox)
If tb IsNot Nothing Then tb.ReadOnly = IsReadOnly

instead of using the TypeOf operator, and then the DirectCast function? As far as I know, both TypeOf and (obviously) DirectCast will perform a cast, so it will be cast twice, whereas the TryCast way will cast only once. If 'tb' isn't derived from a TextBox then it will be Nothing after the cast, so that is more or less equivalent to using the TypeOf operator, isn't it?

I'm sure it will be a minor difference, but perhaps if you have loads and loads of textboxes..?

Am I right about this, or does it not make a difference at all?

[Monkz]

I just have admin rights as a boolean. If Boolean = true, then it lets you modify that data.. As long as boolean = false.. You can see it but not change it.

Thanks for the input guys! i think ill mark this as resolved now!

[Monkz]

I get: IsReadOnly is not declared

[NickThissen]

You must have missed the parameter in the method declaration

[Monkz]

Btw i am also using telerik rad controls.. So they are RadTextBox

It works up until Me.Controls or Me.GetNextControl in the examples by Hack and ForumAccount. But every other mentioning of control, lets me change it to radcontrol with no problem.. But Me.Controls cant be changed to me.RadControls doesnt work.

[Monkz]

You must have missed the parameter in the method declaration

what u mean?

[Monkz]

Ahh this:

Private Sub MakeTBReadOnly(ByVal IsReadOnly As Boolean)

[ForumAccount]

I would just like to add that the For loop ForumAccount uses will not visit nested controls (controls in a panel/groupbox/tabpage, whatever), as he mentioned already, whereas the Do loop used by Hack does.

Also, to both of you, isn't it better to use the following:

Dim tb As TextBox = TryCast(ctrl, TextBox)
If tb IsNot Nothing Then tb.ReadOnly = IsReadOnly

instead of using the TypeOf operator, and then the DirectCast function? As far as I know, both TypeOf and (obviously) DirectCast will perform a cast, so it will be cast twice, whereas the TryCast way will cast only once. If 'tb' isn't derived from a TextBox then it will be Nothing after the cast, so that is more or less equivalent to using the TypeOf operator, isn't it?

I'm sure it will be a minor difference, but perhaps if you have loads and loads of textboxes..?

Am I right about this, or does it not make a difference at all?

You're probably right about that, it seems to make sense. That's how the Windows programmers commonly do it.

[Monkz]

This is what ive been able to get:

Private Sub MakeTBReadOnly(ByVal IsReadOnly As Boolean)
 
        Dim ctrl As RadControl
        Do
 
            If TypeOf ctrl Is RadTextBox Then
                Dim tb As RadTextBox = TryCast(ctrl, RadTextBox)
                If tb IsNot Nothing Then tb.ReadOnly = IsReadOnly
            End If
 
            ctrl = Nothing
        Loop Until ctrl Is Nothing
    End Sub

It wont let me use Me.GetNextControl(Me, True) because it is not a windows form control.

[ForumAccount]

That's not going to work. Actually I think you'll get an exception, what type of project is this? Or are you using a 3rd party form too?

[NickThissen]

Surely a RadTextBox is derived from Control, too? If it's not, I'm stumped.
If it is, then what stops you from simply using what Hack told you, except replacing TextBox with RadTextBox..?

If it really doesn't derive from Control then I think your only option left is to use the For loop as ForumAccount showed you. Check if the RadTextBox controls are directly on the form however, and not in a Panel or any other container control. If they are all in one container control, you can replace "Me" with the name of that container. If they are scattered across different containers, you have to put them into a List(Of RadTextBox) manually (possibly in the constructor or Form_Load event) and loop through that instead.

[Monkz]

Im using a 3rd party tool.. Not a 3rd party form.

[Monkz]

Actually.. This shows no error underlining, but it doesnt do anything either,

 Dim ctrl As RadControl = Me.GetNextControl(Me, True)
        Do

            If TypeOf ctrl Is RadTextBox Then
                Dim tb As RadTextBox = TryCast(ctrl, RadTextBox)
                If tb IsNot Nothing Then tb.ReadOnly = IsReadOnly
            End If
            ctrl = Nothing
        Loop Until ctrl Is Nothing
    End Sub

[Monkz]

This doesnt work for sure...

For Each ctl As Control In Me.Controls

[ForumAccount]

The way you have it now, it's going to test the first control in the tab order then exit the loop, you need to change the bolded line:

Dim ctrl As RadControl = Me.GetNextControl(Me, True)
        Do

            If TypeOf ctrl Is RadTextBox Then
                Dim tb As RadTextBox = TryCast(ctrl, RadTextBox)
                If tb IsNot Nothing Then tb.ReadOnly = IsReadOnly
            End If
            ctrl = Me.GetNextControl(ctl, True)
        Loop Until ctrl Is Nothing
    End Sub

[NickThissen]

And why doesn't it work?

I have never heard about the RadTextBox, but I would be very surprised if it's a control that does not derive in some way or another from the Control class. I it does derive from Control then the code Hack posted should work when you change TextBox to RadTextBox.
You seem to have made a few other changes that break the code completely.

It should be like this:

 Dim ctrl As Control = Me.GetNextControl(Me, True)
        Do

            Dim tb As RadTextBox = TryCast(ctrl, RadTextBox)
            If tb IsNot Nothing Then tb.ReadOnly = IsReadOnly
         
            ctrl = Me.GetNextControl(ctrl, True)
        Loop Until ctrl Is Nothing
    End Sub

Two changes I made are highlighted in bold, the third is that I removed the TypeOf check. It's not strictly wrong to use it, but you should either use TypeOf in combination with DirectCast, as Hack showed you, or use only TryCast, as I showed. A combination works too, but it defeats the point of using my method completely

[ForumAccount]

Hmm... seems I missed a couple things.

[Monkz]

Im using RadTextboxes... When u change it to RadTextbox from textbox it has no problem.. If i move my mouse over RadControl, which i changed Control to, It will say:

Represents a RadControl. RadControl is an Abstract Class and is base class for all Telerik Controls.

[Monkz]

Heres my Current Code:

Imports Microsoft.VisualBasic
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Imports Telerik.WinControls.Themes.Design
Imports Telerik.WinControls.UI
Imports Telerik.WinControls
Imports System.Data.SqlClient
 
Public Class frmuser
 
    Private Sub RadMenuItem3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadMenuItem3.Click
        frmrole.Show()
    End Sub
    Private Sub frmuser_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        MakeTBReadOnly(True)
    End Sub
    Private Sub MakeTBReadOnly(ByVal IsReadOnly As Boolean)
 
        Dim ctrl As Control = Me.GetNextControl(Me, True)
        Do
 
            Dim tb As RadTextBox = TryCast(ctrl, RadTextBox)
            If tb IsNot Nothing Then tb.ReadOnly = IsReadOnly
 
            ctrl = Me.GetNextControl(ctrl, True)
        Loop Until ctrl Is Nothing
    End Sub

It does not make the comboboxes ReadOnly like it should.

[Monkz]

Nvm it works! Though once i move MakeTBReadOnly(True) to an If statement it stops working.

[Monkz]

This worked only when it was not in an if statement:

        Dim ctrl As Control = Me.GetNextControl(Me, True)
        Do

            Dim tb As RadTextBox = TryCast(ctrl, RadTextBox)
            If tb IsNot Nothing Then tb.ReadOnly = IsReadOnly

            ctrl = Me.GetNextControl(ctrl, True)
        Loop Until ctrl Is Nothing

After getting annoyed... I tried this.. Which also worked, but this works in the if statement, where the code above didn't.. Why would this be?

        For Each control In Me.Controls
            If TypeOf control Is RadTextBox Then
                Dim t As RadTextBox = TryCast(control, RadTextBox)

                t.ReadOnly = True
            End If
        Next

[NickThissen]

What If statement, can you show us? The if statement itself should not (and cannot) affect the code inside it, except of course if it prevents it from running in the first place. To see if your loop is running at all, you can place a breakpoint anywhere inside the loop (or just on the start of the loop). When the code execution reaches the line with the breakpoint, it will halt until you tell it to continue. If the execution never halts, then the breakpoint is never reached, and your loop doesn't execute at all.

The second code still has a slight issue, which isn't really important for it's functionality though. It's just a tiny bit 'odd' if you use the TryCast function after you have verified that the type is indeed a RadTextBox.
The TryCast function is actually just the same as the DirectCast function, except for one thing: if the object you are casting cannot be cast to the type you specify, then the DirectCast function will give an error. The TryCast function will not give an error, but it will simply return Nothing (null object).

So, the TryCast function can be used to try to cast an object, and you can see by checking if it's Nothing whether or not it succeeded. If you have already verified that it control is of type RadTextBox, then TryCast cannot fail (at least not for that reason) and so you could just use DirectCast instead.

Now, I don't think it matters whether you use DirectCast or TryCast in your example, but using TryCast enables you to get rid of the TypeOf check, which does an extra cast 'behind the scenes'. So, there is only one cast taking place when you use TryCast (the correct way), while there are two if you use DirectCast in combination with the TypeOf operator.

I realize this is a little off-topic as it has nothing to do with your problem, but you seem to be trying to use it correctly ever since I mentioned it, so I am just correcting you and telling you that it's still not 100% correct (although, as said, it will work equally well).

[Monkz]

So would it be right if i change this:

        For Each control In Me.Controls
            If TypeOf control Is RadTextBox Then
                Dim t As RadTextBox = TryCast(control, RadTextBox)

                t.ReadOnly = True
            End If
        Next

To This:

        For Each control In Me.Controls
          
                Dim t As RadTextBox = TryCast(control, RadTextBox)
                             t.ReadOnly = True
            End If
        Next

[NickThissen]

Nearly. You just need to check if t is not Nothing first, otherwise you cannot access its ReadOnly property. CHecking if t is not Nothing is the equivalent of using the TypeOf check in the first code. The only difference is that the TypeOf check does another cast, which can be bad for memory / speed if used a lot.

You are looking for this:

        For Each control In Me.Controls
          
                Dim t As RadTextBox = TryCast(control, RadTextBox)
                If t IsNot Nothing Then 
                   t.ReadOnly = True
                End If
            End If
        Next

Please note again that you should use the Do loop in combination with GetNextControl to visit every control. The For loop like this will not visit nested controls.