[resolved] [2005] Dynamically created controls get a new ID

I'm not sure why this is happening, but for some strange reason, the asigned ID value of a control i created dynamically in a webpage gets changed - and as such, i can't find it again later to read it's value.

Try this example,... create a ASP.NET project (using VS2005). On the form, drop a PlaceHolder control called phrControls, a Button, and a Label called lblCheck. Then in the code behind window, type this:

Code:

---

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim txtBox As New TextBox
        txtBox.Text = "sample"
        txtBox.ID = "txtBruce"
        phrControls.Controls.Add(txtBox)
    End Sub

    Protected Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        lblCheck.Text = Request.Params("txtBruce")
    End Sub

---

Run it. Type something the text box, and then click the button. Your text is found and display properly.


That works fine for me as well. ;) My problem is when i use a MasterPage. The controls are now inside a ContentPlaceHolder, and when i run the project and click the button, nothing is found. :(

The reason is that my controls have been given a new name! This is what i find when i look at the source code of the HTML page:

Code:

---

<input name="ctl00$cphMainBody$txtBruce" type="text" id="ctl00_cphMainBody_txtBruce" />

---

Why does VB change the name of my control to have all that extra stuff? And how do i fix it?
.
.

Controls are assigned a name based on the control hierarchy they belong to; ASP.NET uses these values to load view state & fire events (on postbacks). You don't need to fix it.

Your immediate problems are:
1) Dynamic controls really should be created in the CreateChildControls method (overridden); the Load event is raised after the control hierarchy is initialised.
2) You're using Request.Params; one of the key points of ASP.NET is the ability to use objects and move away the classic ASP "style". Declare your textbox as a member variable, initialise it once in CreateChildControls, and refer to it by it's instance, e.g.:

Code:

---

private TextBox txtFoo;

protected override CreateChildControls() {
  base.CreateChildControls();

  txtFoo = new TextBox();
  txtFoo.ID = "txtFoo";
  phrControls.Controls.Add(txtFoo);
}

private void Button1_Click(object sender, EventArgs e) {
  this.EnsureChildControls();
  lblCheck.Text = txtFoo.Text;
}

---

You could also use the FindControls method to get a reference to the textbox control. Something like

Code:

---

Protected Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim a As ContentPlaceHolder = Me.Master.FindControl("ContentPlaceHolder1")

    lblCheck.Text = CType(a.FindControl("txtBruce"), TextBox).Text
End Sub

---

If you have a Panel in the ContentPlaceholder and the TextBox is in the Panel you would need to do something like

Code:

---

Dim a As ContentPlaceHolder = Me.Master.FindControl("ContentPlaceHolder1")
Dim b As Panel = a.FindControl("Panel1")
lblCheck.Text = CType(b.FindControl("txtBruce"), TextBox).Text

---

Thanks Axion_Sa. I appreciate that suggestion. While valid, it wouldn't work for me because the dynamic controls are coming from a database, so pre-declaring them (ie: private TextBox txtFoo) wouldn't work in my situation.

BruceVde's suggestion works really well. It's even smart enough to realize that txtQuestion1 and txtQuestion10 are not the same control! :)

Thanks guys.

http://aspnet.4guysfromrolla.com/articles/081402-1.aspx
http://aspnet.4guysfromrolla.com/articles/092904-1.aspx