Finding the previous and next sibling controls

Question

Is there a way to find the previous and next sibling controls in an ASP.net form from code-behind, similar to findControl()?

Sometimes you don't want to assign an ID to a control just so you can do a parent().findControl("ID") in order to find it. I'm tired of coming up with IDs when all I could do is previousControl() or something (a la jQuery).

This would also be useful in situations where you write a general function in order to address several controls which have a similar layout and don't want to address them one by one.

Thanks for any suggestions.

Answer 1

I don't think there is a built in function like that, but it is very easy to extend the Control class and add methods to it like so:

public static Control PreviousControl(this Control control)  
{
   for(int i=0; i<= control.Parent.Controls.Count; i++)
      if(control.Parent.Controls[i].Id == control.Id)
         return control.Parent.Controls[i-1];
}

Of course a bit more handling needs to be done here (if there is no previous control or other scenarios) but i think you get the picture of how this could be done.

After writing this method you can call it like

Control textBox1 = textBox2.PreviousControl();

Answer 2

For posterity, here is the function I ended up writing. Works very well (tested in a real project):

    public static Control PreviousControl(this Control control)
    {
        ControlCollection siblings = control.Parent.Controls;
        for (int i = siblings.IndexOf(control) - 1; i >= 0; i--)
        {
            if (siblings[i].GetType() != typeof(LiteralControl) && siblings[i].GetType().BaseType != typeof(LiteralControl))
            {
                return siblings[i];
            }
        }
        return null;
    }

To be used like this:

Control panel = textBox.PreviousControl();

and for next control:

    public static Control NextControl(this Control control)
    {
        ControlCollection siblings = control.Parent.Controls;
        for (int i = siblings.IndexOf(control) + 1; i < siblings.Count; i++)
        {
            if (siblings[i].GetType() != typeof(LiteralControl) && siblings[i].GetType().BaseType != typeof(LiteralControl))
            {
                return siblings[i];
            }
        }
        return null;
    }

The advantage of this solution over that of Atzoya is that, first, you don't need the original control to have an ID since I do the search based on instance. Second, you have to know that ASP.net generates several Literal controls in order to render your static HTML in between your "real" controls. That's why I skip them, or you will keep matching junk. Of course the downside of this is you can't find a control if it's a Literal. This limitation was not a problem in my use.