How do I change a textbox backcolor based on the result of a combobox

Question

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Need help with this:

1. I have a cbDroppedEarly combo box - choices are YES or NO - defaulted to NO
2. I have a tbLinehaulPaid text box

I would like to change the background color of tbLineHaul only if cbDroppedEarly = "YES"
else keep the default color - does not matter what value is in the tbLineHaulPaid - the default is $0.00 as BackColor is solely based on the combobox value.

Can this be done? I tried the code below and it will not work. If not any suggestions would be greatly helpful and appreciated.

What I have tried:

VB

Private Sub tbLinehaulPaid_Change()
    Select Case cbDroppedEarly.ToString
        Case "YES" : tbLinehaulPaid.BackColor = Color.Teal
        Case Else : tbLinehaulPaid.BackColor = Color.WhiteSmoke
    End Select
End Sub

Posted 7-Apr-16 20:37pm

K3JAE

Updated 8-Apr-16 7:47am

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2 solutions

Solution 1

You have to use the SelectedIndexChanged event of your ComboBox, and change the BackColor property of the TextBox accordingly.

VB

Private Sub cbDroppedEarly_SelectedIndexChanged(ByVal sender as Object, ByVal e As EventArgs)
   Dim index As Integer = cbDroppedEarly.SelectedIndex
   Select Case index
      Case 0 : tbLinehaulPaid.BackColor = Color.Teal
      Case Else : tbLinehaulPaid.BackColor = Color.WhiteSmoke
   End Select
End Sub

Hope this helps.

Posted 7-Apr-16 20:56pm

phil.o

Comments

K3JAE 8-Apr-16 14:02pm

I changed the code to what you have above. Unfortunately this made no change to my tbLineHaulPaid background color when I changed the cbDroppedEarly to "yes."

Did I miss something?

phil.o 9-Apr-16 3:52am

You have to associate the event handler you created to the combobox event.
Creating Event Handlers on the Windows Forms Designer[^]
Applied to your case:
To create an event handler in C# or C++
Click the ComboBox control.
In the Properties window, click the Events button.
In the list of available events, find the SelectedIndexChanged event.
In the box to the right of the event name, select the cbDroppedEarly_SelectedIndexChanged method.
Then test again.
You should also have a look at Event Handling in Windows Forms[^]

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Ivan_FM · Accepted Answer · 2016-04-08T07:35:00

Solution 3

I guess the only thing wrong in your original code was this:

VB.NET

Private Sub tbLinehaulPaid_Change()
    Select Case cbDroppedEarly.ToString 
    Select Case cbDroppedEarly.Selecteditem.ToString
        Case "YES" : tbLinehaulPaid.BackColor = Color.Teal
        Case Else : tbLinehaulPaid.BackColor = Color.WhiteSmoke
    End Select
End Sub

In order to make work the solution 2, make sure that the "YES" value is the same that the index that you have selected.

If you say that still not working... mmm... then, Make sure that you are using properly the event "cbDroppedEarly.selctedindexchanged". Take a look at the control events, maybe the link between the code and the control has broken.

Posted 8-Apr-16 7:35am

Ivan_FM

Updated 8-Apr-16 7:59am

v2

Comments

K3JAE 8-Apr-16 14:01pm

Using the original code and changed as noted, still no luck. the tbLineHaulPaid when I choose YES in the combobox.

Question - does the tbLineHaulPaid box have to be a rich text box for this to work?

Ivan_FM 8-Apr-16 14:02pm

If you say that still not working... mmm... then, Make sure that you are using properly the event "cbDroppedEarly.selctedindexchanged". Take a look at the control events, maybe the link between the code and the control has broken.

K3JAE 8-Apr-16 14:28pm

I apologize as my coding skills are weak at best. I am not sure what you refer to by "Take a look at the control events, maybe the link between the code and the control has broken."

Ivan_FM 8-Apr-16 14:36pm

No problem. Take a look here TextBox Events (System.Windows.Forms)[^]

I think the problem is in the event. Try this again.

Private Sub cbDroppedEarly_SelectedIndexChanged(ByVal sender as Object, ByVal e As EventArgs) handles cbDroppedEarly.SelectedIndexChanged
Select Case cbDroppedEarly.Selecteditem.ToString
Case "YES" : tbLinehaulPaid.BackColor = Color.Teal
Case Else : tbLinehaulPaid.BackColor = Color.WhiteSmoke
End Select
End Sub

Note the "handles cbDroppedEarly.SelectedIndexChanged". This links the event to the textbox.

K3JAE 8-Apr-16 14:40pm

EXCELLENT. That was it. I was going to ask if a "handle" was needed.

Kudos!!

Ivan_FM 8-Apr-16 14:41pm

;)

K3JAE 8-Apr-16 14:53pm

One last item... If I wanted to change multiple textboxes as above, cannot remember how to add additional boxes without making more events...

Example, change tbLineHaulPaid AndAlso tbFuelSurchargePaid - Cannot remember how to add multiple items to the case.

Ivan_FM 8-Apr-16 14:56pm

Try this:

Select Case cbDroppedEarly.Selecteditem.ToString
Case "YES"
tbLinehaulPaid.BackColor = Color.Teal
tbFuelSurchargePaid.BackColor = Color.Teal
Case Else
tbLinehaulPaid.BackColor = Color.WhiteSmoke
tbFuelSurchargePaid.BackColor = Color.WhiteSmoke
End Select

K3JAE 8-Apr-16 15:02pm

Correct, I remembered right before your last text came in and had it figured out and working. Thanks again. All good and happy now!! Have a great day!

Ivan_FM 8-Apr-16 15:06pm

Ok, keep on trying and learning ;)

Have a great day too!