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[jtykal]

I'm just starting to dabble in VB (using Express v8), and would like to have a list of Labels showing the open/close status of each door in my house (DoorState1, DoorState2, DoorState3, etc.). Is there a way to reference a Form Control object (in this case, a Label) using a string variable instead of explicitly naming it? I'm not clear on the terminology I want to use here -- reference, dereference, pointer, etc. come to mind from my programming days -- but that was 20+ years ago!   

What I'm looking to do is replace code that looks like this:

                    Select Case DoorNum
                        Case 0
                            DoorState0.Text = "OPEN"
                            DoorState0.ForeColor = Drawing.Color.Green
                        Case 1
                            DoorState1.Text = "OPEN"
                            DoorState1.ForeColor = Drawing.Color.Green
                        Case 2
                            DoorState2.Text = "OPEN"
                            DoorState2.ForeColor = Drawing.Color.Green
                        Case 3
                            DoorState3.Text = "OPEN"
                            DoorState3.ForeColor = Drawing.Color.Green

...with something cleaner that can append the DoorNum to the end of a fixed string and use the resulting string variable as the name of the Label I want to update.  How do I get a pointer to an object in the current Form f I know the name (and class) of the object??

                    Dim testField As String
                    Dim testObj As System.Windows.Forms.Label
                    testField = "DoorState" & DoorNum
                    testObj = ' get the Label named testField in the current Form
                    testObj.Text = "OPEN"
                    testObj.ForeColor = Drawing.Color.Green

I hope that makes sense... Any thoughts? 

Thanks in advance...
jim

[-Bill- (of wgjohns.com)]

Open up the VB help, and search the index for "control arrays".

I think this will tell you what you need to know.

 

[EL34]

It's early and my brain is slow but I have a code snipet from a recent project that may help.
It searches through the list of controls looking for a picturebox using text and a variable to create a control name

c.Name is the control name in my form1.designer.vb file
PictureBoxClicked is a variable with a number, say it is a 10 in this case

search for a control called "PictureBox & "10" - or PictureBox10

Code: [Select]

        ' find the picturebox that was clicked and change the volume level graphic
        For Each c As Control In Me.Controls
            If c.Name = "PictureBox" & PictureBoxClicked Then
                Dim PictureBoxName As System.Windows.Forms.PictureBox
                PictureBoxName = CType(c, PictureBox)

                'This code sets a small .png image for the picturebox that was clicked
                PngImage = VolumeArray(Volume) ' get a .png image
                PictureBoxName.Image = Image.FromFile(FolderPath & "Images\" & PngImage)

            End If
        Next
 
The best place to get VB express help is here.
http://social.msdn.microsoft.com/forums/en-US/Vsexpressvb/threads/

[EL34]

Ok, I am awake now, I think this is what you want.
I created a simple form that has a button and 3 labels
Pressing the button each time turns on the forecolor green of each label
It also returns the old label to the color black.

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        LabelName2 = Label1 ' assign a value to LabelName2
    End Sub

    Dim LabelName1 As System.Windows.Forms.Label
    Dim LabelName2 As System.Windows.Forms.Label
    Dim Count As Integer = 0

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Count = Count + 1
        If Count = 4 Then Count = 1

        If LabelName2.ForeColor = Color.Green Then
            LabelName2.ForeColor = Color.Black ' return old label to black
        End If

        For Each c As Control In Me.Controls
            If c.Name = "Label" & Count Then
                LabelName1 = CType(c, Label)
                LabelName1.ForeColor = Color.Green ' new label is now green
                LabelName2 = LabelName1 ' old label = new label
            End If
        Next

        TextBox1.Text = "Label # " & Count ' display label number

    End Sub

End Class

[jtykal]

EL34 and -Bill-: Thank you both! 
I did eventually discover the looping method to search for a control name. I didn't like looping through the 50+ controls on my form to find the one I needed to update; but I learned that if I used a group box to house the similar controls, I could just loop through the 5 or 6 controls inside that group box!  This works perfectly, but I'm still hoping to avoid the search loop entirely. I need to investigate -Bill-'s suggestion regarding control arrays. A quick search revealed that control arrays were a VB6 feature and are no longer supported in VB2008, but there was a reference to some other mechanism in VB2008 that rendered control arrays obsolete. Need to dig deeper there...
Thanks again!

[EL34]

...with something cleaner that can append the DoorNum to the end of a fixed string and use the resulting string variable as the name of the Label I want to update

I looked back at your original post above
If you don't need to loop through controls, and just want to address the exact label you need to change the forecolor on

x is a variable name for the label suffix
In this example, x=2 and so the forecolor will be changed to green on Label2: "Label" & x = Label2

like this:

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

        Dim x As Integer = 2 ' this would be the label number you want to update

        Dim LabelName As Label = Me.Controls("Label" & x)

        LabelName.ForeColor = Color.Green

    End Sub

[jtykal]

That's EXACTLY what I was looking for, EL34!  Thank you! 

[EL34]

That's what I thought, that's why I re-read your post

I was confused by the control array thing because I thought I remembered you wanting to do something much simpler.

But it was 5:30 this morning when I first read your post and  my brain was in low gear at the time.