Convert String to Control

[DroopyPawn]

Is it possible to convert a string into a control?
Dim Ctrl as string = "DataGridView"
Dim Index as integer = "1"
Dim g as DataGridView = DirectCast(Ctrl & Index, DataGridView)

and then access the properties of the Grid...
g.BackColor = Color.Red
g.Left = 3
etc.

I'm pretty sure it's possible but nothing I've tried works.

[Atheist]

Not convert it, but you can specify the get the control from the containers collection by its name:

Dim g As DataGridView = DirectCast(Me.Controls("DataGridView1"), DataGridView)

But if you really think you need to use this method, you will need to redesign your code.

[kleinma]

you can do it by accessing the control by name from the forms controls collection like this:

        Dim Ctrl As String = "DataGridView"
        Dim Index As Integer = 1
        Dim g As DataGridView = DirectCast(Me.Controls(Ctrl & Index.ToString), DataGridView)

note that the forms controls collection only holds controls directly on the form, so if the DGV is in a panel or another container control like that, you need to use the controls collection of that container, and not the form.

[DroopyPawn]

I suppose that if the control was inside a container on the form (like in a TabControl) that would affect the code wouldn't it?

[kleinma]

yes instead of the keyword Me (which indicates the form) you would use the variable name for the TabPage (not the TabControl) that the given datagridview is on.

Dim g As DataGridView = DirectCast(TabPage1.Controls(Ctrl & Index.ToString), DataGridView)

[cnuser1]

thanks you so much, this info. is good for me.

[iexpress]

I found a shortcut! and its superly duperly dynamic!

Dim s As String = "textbox"
Dim c As Object

If s = "textbox" Then
c = New TextBox
c.Text = "This is a textbox"
c.Location = New System.Drawing.Point(200, 50)
c.Size() = New System.Drawing.Size(70, 20)

Me.Controls.Add(c)
End If

[.paul.]

I found a shortcut! and its superly duperly dynamic!

Dim s As String = "textbox"
Dim c As Object

If s = "textbox" Then
c = New TextBox
c.Text = "This is a textbox"
c.Location = New System.Drawing.Point(200, 50)
c.Size() = New System.Drawing.Size(70, 20)

Me.Controls.Add(c)
End If

you misunderstood this thread

[Niya]

If you want to create a class via a string that represents its type name you can use this:-

'
    Public Function CreateClass(ByVal className As String) As Object
 
        Dim asms() As Assembly = AppDomain.CurrentDomain.GetAssemblies
 
        For Each Asm As Assembly In asms
            Dim types = Asm.GetTypes
 
            For Each T As Type In types
                If T.Name.Equals(className, StringComparison.OrdinalIgnoreCase) Then
                    Return Activator.CreateInstance(T)
                End If
            Next
 
        Next
 
        Throw New Exception("Type not found")
    End Function

Here is a version using Linq:-

'
    Public Function CreateClass(ByVal className As String) As Object
        Dim asms() As Assembly = AppDomain.CurrentDomain.GetAssemblies
 
        Dim typeSought() As Type = (From Asm In asms _
                                Let types As Type() = Asm.GetTypes _
                                Let found As Type = Array.Find(Of Type)(types, Function(t) t.Name.Equals(className, StringComparison.OrdinalIgnoreCase)) _
                                Where found IsNot Nothing Select found).ToArray
 
        If typeSought.Length > 0 Then
            Return Activator.CreateInstance(typeSought(0))
        End If
 
        Throw New Exception("Type not found")
    End Function

Use it like:-

'
        Dim tb As TextBox = CreateClass("textbox")
        Dim dg As DataGridView = CreateClass("datagridview")
 
 
        Me.Controls.Add(tb)
        Me.Controls.Add(dg)

[timjohn]

I've read this with interest but still can't get what I want to do to work.
My requirement is...
Get a string from a database say dbstr which = "cmd2"
Create a new instance of a form and then Performclick on the control button named btn2 on that form.
I'm struggling with the Directcast statement to do this. I've tried

Dim dbstr As String
Dim btn As New Button
Dim ssga As New sggAcs //(sggAcs is a project form)
dbstr = "cmd2"
btn = DirectCast(ssga.Controls(dbstr), Button)

If I then try

ssga.btn.PerformClick()

vb tells me that btn is not a member of sggAcs
I use this method a fair bit to change the screen colours etc. depending on what the user is doing so any pointers to my errors would be much appreciated.

[kleinma]

is the button in any sort of container control, like a panel or groupbox?

[timjohn]

Yes it's in a panel.
does that mean I should have put
ssga.panelname.btn.PerformClick()
I'll go and try it.
Thanks.

[timjohn]

Panel is called pnl2 so I tried this

Dim dbstr As String
Dim btn As New Button
Dim ssga As New sggAcs
dbstr = "cmd2"
btn = DirectCast(ssga.Controls(dbstr), Button)
MsgBox(ssga.pnl2.btn.text)

blue squiggly line under ssga.pnl2.btn - Error List gives "btn is not a member of System.Windows.Forms.Panel"
Bother!

i've now tried this - code is in a button_click event on main form.

Dim dbstr As String
Dim ssga As New sggAcs
dbstr = "cmd2"
Me.Text = ssga.pnl2.Controls(dbstr).Text

when I click the button in main form the title bar changes to the text of the button in the form sggAcs, so I can access the text property of a control on another form without using directcast BUT when I try this which is what I really want to do...

ssga.pnl2.Controls(dbstr).performclick()

I get an error message - performclick is not a member of 'System.Windows.Forms.Control'
I'm obviously missing something important here but can't figure out what.
Any pointers much appreciated.

[.paul.]

directcast(ssga.pnl2.Controls(dbstr), Button).performclick()

[timjohn]

Hi,
Tried that and as soon as I clicked the button on the main form I got this in the immediate window..
A first chance exception of type 'System.NullReferenceException' occurred in Gtacs.exe
Odd as your line of code didn't produce any errors and I don't understand the .exe bit as I'm running in vb2010 debug mode. However Gtacs is the project name, just not compiled yet.

[.paul.]

at the time you got that error, had you created the dbstr button?

[.paul.]

i need to see all of your relevant code.
i'm not sure if you're adding a button in code or it already exists, + you're trying to refer to it by a string

[timjohn]

Hi Paul,
Was in middle of writing to you when you asked for code, so scrapped last post and send this in it's place. Hope it's what you need.
Here is the code in the main form.

Bit at top of form is this.
Option Strict Off
Option Explicit On
Imports VB = Microsoft.VisualBasic
Then the relevant button is this.
Private Sub cmd2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd2.Click
    Dim dbstr As String
    Dim ssga As New sggAcs
    dbstr = "cmd3"
    DirectCast(ssga.Controls(dbstr), Button).PerformClick()
End Sub

This is the code for the other form where the buton to be clicked is..

Friend Class sggAcs
    Inherits System.Windows.Forms.Form
    Private Sub cmd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd1.Click, cmd2.Click, cmd3.Click
        If sender.Tag <> gtType Then
            gtType = sender.tag
            gtCode = Trim(gtID) & sender.tag
            If sender.tag = "g" Then
                gtHead = "General"
            ElseIf sender.tag = "c" Then
                gtHead = gtCamp
            Else
                gtHead = "Fundraising"
            End If
            MainGtacs.Text = "Gtracs - " & gtHead & " Accounts - " & gtIdent
            Me.Dispose()
        Else
            Me.Dispose()
        End If
    End Sub
End Class.

There is more to go in but it's not there yet.
BTW, I'm trying to convert(re-writing) a system from VB6. Then I just used the index of an array, not in vb2010 though!

[.paul.]

ok. it seems you're creating + referring to a new instance of your form, instead of the open instance you should be referring to. here's an example using a form (Form2) + a button (Button1):

DirectCast(My.Application.OpenForms("Form2").Controls("Button1"), Button).PerformClick()

[.paul.]

BTW... you can use an array of buttons in vb.net, but in a different way to the vb6 control array:

Public Class Form1
 
    Dim btns() As Button
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        btns = New Button() {Button1, Button2, Button3}
    End Sub
 
End Class

[.paul.]

are you intending to open a new form + click cmd3?

why not just use [formName].[buttonName].PerformClick() ?

[timjohn]

Hi Paul,
Working backwards
(21) I only have the button name in a string variable so [formName].[buttonName].PerformClick() doesn't work when I replace [buttonName] with a variable, get the error 'dbstr' is not a member of 'Gtacs.sggAcs'.
(20) Thanks for that I'll have a play and see.
(19) I get an error 'OpenForms' is not a member of 'Gtacs.My.MyApplication'

Sorry to be causing all this, I really thought I was asking something simple (well it was in VB6)- click a control button on a second form & carry out the code on the button click, with the user never seeing the second form. All it took was 3 lines

Load sggAcs
sggAcs.Command3(gtAcNo).Value = True
Unload sggAcs

where gtAcNo was an integer.

[timjohn]

Think I've got it - not sure if it's the correct way/good coding but it seems to work.

Add

Public Shared btns() As Button

to the Target Form below Inherits statement.

Then Add

btns = New Button() {cmd1, cmd2, cmd3}

to the Target Forms Load event.

Then use

Dim dbstr As Integer
sggAcs.Show()
dbstr = 2 // dbstr will be filled from the database(-1) & it becomes index of btns.
DirectCast(sggAcs.btns(dbstr), Button).PerformClick()

in the calling form.
If you know a better way I'd appreciate it.

Thanks are due for all your help in pointing me in the right direction.

[.paul.]

no need to cast:

sggAcs.btns(dbstr).PerformClick()

[timjohn]

Got it, thanks Paul, won't have such a late night tonight.