Question

I want to write a custom control involving a DropDownList and a TextBox.
Actually, I want to dynamically render DropDownList and TextBox.
For example: when a user clicks a Checkbox, the Textbox will change to a DropdownList. On the other hand, when a user deselects the Checkbox, the Dropdownlist will change to a Textbox.

I know this can be done using two controls, which sets the visibility for both control. But can I do it on a custom control?

Answer 1

If you still want to go with that approach, here is your code.

In Design File:-

 <asp:CheckBox ID="CheckBox1" runat="server" AutoPostBack="True"
 oncheckedchanged="CheckBox1_CheckedChanged" />

 <div id ="control" runat="server">

 </div>

In Code Behind File:-

protected void Page_Load(object sender, EventArgs e)
{
  if (!Page.IsPostBack)
   {
     TextBox txt = new TextBox();
     txt.ID = "txt";
     control.Controls.Add(txt);
   }
}
protected void CheckBox1_CheckedChanged(object sender, EventArgs e)
{
   if (CheckBox1.Checked)
    {
       for (int ix = this.Controls.Count - 1; ix >= 0; ix--)
           if (this.Controls[ix] is TextBox) this.Controls[ix].Dispose();

       DropDownList ddl = new DropDownList();
       ddl.ID = "ddl";

      control.Controls.Add(ddl);
    }
    else
    {
      for (int ix = this.Controls.Count - 1; ix >= 0; ix--)
          if (this.Controls[ix] is DropDownList) this.Controls[ix].Dispose();

       TextBox txt = new TextBox();
       txt.ID = "txt";

       control.Controls.Add(txt);
    }
}

Hope this is what you were looking for.