If what you are only attempting to do is find the controls, simply change
your retval from ControlCollection to ArrayList and your code will work as
expected. The problem you are encountering relates to the framework
enforcing that a given control can only exist in one ControlCollection and
once you do the Add() into your ControlCollection it is removing it from
the original ControlCollection you are interating on. Thus the cause for
your error.
Chad
On Wed, 9 Jul 2003 11:13:44 -0400, Bryan, Jason (Contractor)
<[EMAIL PROTECTED]> wrote:
>Hi all!
>
>I am trying to discover and place into a ControlCollection all the
controls
>on a web page that match a particular type or begin with a particular
name.
>To do this, I've written a function that will go through the
>ControlCollection passed to it and add the controls that match the
condition
>to another ControlCollection, as shown:
>
>private System.Web.UI.ControlCollection FindControls(string ControlName,
>System.Web.UI.ControlCollection ControlSet)
>{
> System.Web.UI.ControlCollection retval = new
>System.Web.UI.ControlCollection(new System.Web.UI.Control());
> foreach (System.Web.UI.Control thing in ControlSet)
> {
> if (thing.ID != null)
> if (thing.ID.StartsWith(ControlName))
> retval.Add(thing);
> if (thing.HasControls())
> FindControls(ControlName, thing.Controls, ref
>retval);
> }
> return retval;
>}
>
>private void FindControls(string ControlName,
>System.Web.UI.ControlCollection ControlSet, ref
>System.Web.UI.ControlCollection retval)
>{
> foreach (System.Web.UI.Control thing in ControlSet)
> {
> if (thing.ID != null)
> if (thing.ID.StartsWith(ControlName))
> retval.Add(thing);
> if (thing.HasControls())
> FindControls(ControlName, thing.Controls, ref
>retval);
> }
>}
>
>When I try running this, the following exception is thrown:
>
>"The list that this enumerator is bound to has been modified. An
enumerator
>can only be used if the list doesn't change."
>
>With a stack trace of:
>
>[InvalidOperationException: The list that this enumerator is bound to has
>been modified. An enumerator can only be used if the list doesn't change.]
> System.Web.UI.ControlCollectionEnumerator.MoveNext() +112
> cs.webcontrols.FindControls(String ControlName, ControlCollection
>ControlSet, ControlCollection& retval) in
>c:\inetpub\wwwroot\cs\webcontrols.cs:75
> cs.webcontrols.FindControls(String ControlName, ControlCollection
>ControlSet) in c:\inetpub\wwwroot\cs\webcontrols.cs:67
> cs.webcontrols.Page_Load(Object sender, EventArgs e) in
>c:\inetpub\wwwroot\cs\webcontrols.cs:28
> System.EventHandler.Invoke(Object sender, EventArgs e) +0
> System.Web.UI.Control.OnLoad(EventArgs e) +67
> System.Web.UI.Control.LoadRecursive() +35
> System.Web.UI.Page.ProcessRequestMain() +731
>
>When I trace through, the error occurs when I hit the first match, do a
>.Add, and loop around for the next control. So, I put more watches on the
>variables around what .NET claimed was the offending line. I watched it
run
>through and found that when the .Add method was called, it didn't copy a
>reference to the control as I would have expected...it MOVED the control
>from the parent ControlCollection to the new ControlCollection.
>
>So, I tried to fool .NET by adding a function:
>
>private void addControl(System.Web.UI.Control inControl, ref
>System.Web.UI.ControlCollection retval)
>{
> retval.Add(inControl);
>}
>
>and I change from calling .Add to:
>
> addControl(thing, ref retval);
>
>thinking that because I was passing copies, .NET wouldn't be able to
modify
>the original.
>
>Wrong.
>
>I ran the modified code and watched .NET do the same thing all over again.
>
>So...what is going on?? It appears that System.Web.UI.ControlCollection
(s)
>passes a pointer and not a copy. To add to that, the only way to copy
this
>class is by calling the ".CopyTo" method which puts the control into a
>System.Array. This doesn't seem right either.
>
>I must be going about this the hard way. Anyone have any suggestions or
>ideas?
>
>TIA!
>Jason Bryan
