Change Label ForeColor When TextBox Value Changes

  • Thread starter Thread starter crjunk
  • Start date Start date
C

crjunk

Hi Everyone,

I have a web form that I would like to enhance. What I'd like to do
is this:
A user adds/edits the text in a textbox. I want the adjoining label to
change color.

Example:
User edits text in txtCaseNumber. The cursor leaves txtCaseNumber.
Code executes and turns lblCaseNumber text from black to red.

Here is what I've come up with so far:

Protected Sub txtCaseNumber_TextChanged(ByVal sender As Object, ByVal
e As System.EventArgs) Handles txtCaseNumber.TextChanged

ChangeLabelColor(sender)

End Sub

Private Sub ChangeLabelColor(ByVal TextBox)
Dim labelID As String = TextBox.ID.replace("txt", "lbl")
Dim ctrl As New Control
Dim ctrlNameText As Label

For Each ctrl In Page.FindControl("aspnetForm").Controls
If TypeOf (ctrl) Is Label And (ctrl.ID.ToString.Trim =
labelID.Trim) Then
ctrlNameText = ctrl
ctrlNameText.ForeColor = Drawing.Color.Red
End If
Next

End Sub


The code bombs out on the For Each ctrl statement.
In debug mode, I'm receiving the following messages:
NullReferenceException was unhandled by user code.
Object reference not set to an instance of an object.

Can anyone offer some suggestions?

Thanks,

CR Junk
 
Page.FindControl("aspnetForm") is returning null, so accessing .Controls
from it thows an error. either there is no Control named "aspnetForm", or it
not an immediate child of the Page.

if label is a sibling of the textbox, then just do a FindControl by name. to
find it, the label must have a runat="server", so you could just access it by
name.

the onchanged will not fire until a postback, so you must set AutoPostBack =
true, will will then cause a postback on th onblur client event.

this easily done in javascript without requiring a postback, and give a much
better experince to you users.




-- bruce (sqlwork.com)
 
Page.FindControl("aspnetForm") is returning null, so accessing .Controls
from it thows an error. either there is no Control named "aspnetForm", or it
not an immediate child of the Page.
Click to expand...


I have a question about this. Originally, I had
Page.FindControl("form1") instead of aspnetForm. The MasterPage that
I am using has "form1" listed in the html source, but when I run my
default.aspx web form and look at the source code through my browser,
it has "aspnetForm" listed. Which form name should I be using?

if label is a sibling of the textbox, then just do a FindControl by name. to
find it, the label must have a runat="server", so you could just access it by
name.
Click to expand...


I commented out my For statement, verified lblCaseNumber had
runat="server" and tried the following:

Dim lbl As Label = CType(Page.FindControl("lblCaseNumber"),
Label)
lbl.Text = "HELLO WORLD"

but I am still receiving: "Object Reference not set to an instance of
an object". Is this the proper way to use the FindControl stament?

the onchanged will not fire until a postback, so you must set AutoPostBack =
true, will will then cause a postback on th onblur client event.
Click to expand...


I verified that AutoPostBack = True for txtCaseNumber

this easily done in javascript without requiring a postback, and give a much
better experince to you users.
Click to expand...

Normally, I would try doing this ne javascript, but I'm using this
code as somewhat of a test so that I can expand it to do a lot of
other formatting, validating, etc....

Thanks for your help!
CR Junk
 
Page.FindControl("aspnetForm") is returning null, so accessing .Controls
from it thows an error. either there is no Control named "aspnetForm", or it
not an immediate child of the Page.
Click to expand...


I have a question about this. Originally, I had
Page.FindControl("form1") instead of aspnetForm. The MasterPage that
I am using has "form1" listed in the html source, but when I run my
default.aspx web form and look at the source code through my browser,
it has "aspnetForm" listed. Which form name should I be using?

if label is a sibling of the textbox, then just do a FindControl by name. to
find it, the label must have a runat="server", so you could just access it by
name.
Click to expand...


I commented out my For statement, verified lblCaseNumber had
runat="server" and tried the following:

Dim lbl As Label = CType(Page.FindControl("lblCaseNumber"),
Label)
lbl.Text = "HELLO WORLD"

but I am still receiving: "Object Reference not set to an instance of
an object". Is this the proper way to use the FindControl stament?

the onchanged will not fire until a postback, so you must set AutoPostBack =
true, will will then cause a postback on th onblur client event.
Click to expand...


I verified that AutoPostBack = True for txtCaseNumber

this easily done in javascript without requiring a postback, and give a much
better experince to you users.
Click to expand...

Normally, I would try doing this ne javascript, but I'm using this
code as somewhat of a test so that I can expand it to do a lot of
other formatting, validating, etc....

Thanks for your help!
CR Junk
 
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