Accessing the Controls of a User Control?

Aaron Edwards · June 16th, 2006, 09:59 AM

Is it possible to Access the controls inside a User Control from the main page?

I've tried this, and it doesn't seem to work:

(Main Page-codebehind)

Dim tbCCNumber As TextBox = CType(Me.PaymentPanel1.FindControl("tbCCNumber"), TextBox)

In this case, PaymentPanel1 is an instance of a User Control called PaymentPanel, which I've referenced on the main page as follows:

<%@Reference Control="~/PaymentPanel.ascx" %>

Do I need to expose the constituent controls on the user control as properties or something like that?

Thanks.

Aaron

Aaron Edwards · June 16th, 2006, 10:09 AM

Okay I did some research, and found that to access the user control's constituent controls, they must be declared as public.

Now my question is: how do you do this in ASP.NET 2.0? In 1.1 this was easy, because they were visibly declared at the top of the codebehind. Now in 2.0 they are only declared in the aspx page and I can't figure out how to add a Public accessor to the declaration.

Thanks.

Aaron

Imar · June 16th, 2006, 10:34 AM

You could add a public property to your control, that gives access to your server control, like this:

public TextBox UserNameBox
{
  get
  {
    return txtUserName;
  }
}

This way, the page can access the control, but not completely change it. You can, however, change its own properties like its Text property. If you want to be able to change the entire box, implement a set accessor as well.

Now you can access the properties like this:

MyUserControl.UserNameBox.Text = "SomeText";

HtH,

Imar
---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.
Author of ASP.NET 2.0 Instant Results and Beginning Dreamweaver MX / MX 2004

Aaron Edwards · June 16th, 2006, 03:15 PM

Thanks Imar,

The only control on the User control that I'll need to change will be a dropdown list. I'll need to be able to execute a RemoveAt method on it. Should I just write my own method on the user control which does that?

Aaron

Imar · June 16th, 2006, 03:30 PM

No need for that. The public control property allows you to call that method directly:

MyUserControl.MyDropDown.RemoveAt(0);

should work as well....

Imar
---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.
Author of ASP.NET 2.0 Instant Results and Beginning Dreamweaver MX / MX 2004

Aaron Edwards · June 16th, 2006, 04:33 PM

Thanks Imar,

It didn't seem to like me removing listbox items from the page level. Said my reference wasn't instantiated. Do you think this is because the property I set in the user control was read only? E.g.

    Public ReadOnly Property ExpirationMonth() As DropDownList
        Get
            Return Me.ddlExpirationMonth
        End Get
    End Property

Imar · June 16th, 2006, 07:22 PM

Hi Aaron,

Not sure what's going wrong in your situation. Are you creating controls dynamically?? Here's what I did (and what works for me):

User Control Markup (Test.ascx)

Code:

<%@ Control Language="VB" AutoEventWireup="false" CodeFile="Test.ascx.vb" Inherits="MyControl" %>
<asp:DropDownList ID="DropDownList1" runat="server">
  <asp:ListItem>1</asp:ListItem>
  <asp:ListItem>2</asp:ListItem>
  <asp:ListItem>3</asp:ListItem>
  <asp:ListItem>4</asp:ListItem>
</asp:DropDownList>

User Control Code Behind (Test.ascx.vb)

Code:

Partial Class MyControl
  Inherits System.Web.UI.UserControl

  Public ReadOnly Property MyDropDown() As DropDownList
    Get
      Return Me.DropDownList1
    End Get
  End Property

End Class

Page with the control: (Test.aspx)

Code:

      <uc1:Test ID="Test1" runat="server" />
      <asp:Button ID="Button1" runat="server" Text="Button" /></div>

where uc1:Test refers to my custom control called MyControl in the file Test.ascx.

Code behind of the page: (Test.aspx.vb)

Code:

Partial Class Test
  Inherits System.Web.UI.Page

  Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
    Me.Test1.MyDropDown.Items.RemoveAt(2)
  End Sub
End Class

When I run this page and click the button, one item is removed from the list.

Does this work for you?

Imar
---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.
Author of ASP.NET 2.0 Instant Results and Beginning Dreamweaver MX / MX 2004