ValidationProperty not returning entered value for textbox in custom control

Question

hi

I have a custom control, (relevant code at the bottom) it consists of some text/links and a hidden textbox (rather than a hidden input). when rendered, the user via another dialog and some JS sets the value of the textbox to an integer and clicks submit on the form. i am trying to assure that the user has entered a number (via the JS) and that the textbox is not still set to its default of "0" the requiredfieldvalidator works just fine, if i dont change the value it spots it on the client and fills the validation summary on the page with the appropriate message.

unfortunately when i do fill the textbox, the validator also rejests the post as the controls textbox text value is still set to "0", even though on the form it has changed. clearly i am doing something wrong.. but cant work out what it is? could someone enlighten me please, this is driving me potty

if i step through the code, when the get of the mediaidtext is hit,the findcontrol finds does not the textbox, if i inspect the controls collection however i can find the textbox, but its value is still "0"

it also seems that when findcontrol is called, the createchildcontrols is called again - thus resetting the value back to "0" there.. ! how can i ever assure the control realises that the textbox value has changed?

many thanks code below

nat

[ValidationProperty("MediaIdText")]

public class MediaLibraryFileControl: CompositeControl {

private int mediaId = 0;
public int MediaId {
    get { return mediaId; }
    set { mediaId = value; }
}

public string MediaIdText
{
    get
    {
                string txt="0";
                foreach (Control c in Controls)
                {
                    if (c.ID == this.UniqueID + "_hidden")
                    {
                        txt = ((TextBox)c).Text;
                        MediaId = Convert.ToInt32(txt);
                        break;
                    }
                }
                return txt
    }
}

       protected override void CreateChildControls()
{
    this.Controls.Add(new LiteralControl("<span>"));
    this.Controls.Add(new LiteralControl("<span id=\"" + TextControlName + "\">" + getMediaDetails() + "</span>"));

    TextBox tb = new TextBox();
    tb.Text = this.MediaId.ToString();
    tb.ID = this.UniqueID + "_hidden";
    tb.CssClass = "hidden";
    this.Controls.Add(tb);

    if (Select == true)
    {
        this.Controls.Add(new LiteralControl(string.Format("&nbsp;[<a href=\"javascript:{0}(this,'{1}','{2}')\" class=\"select\">{3}</a>]", dialog, this.UniqueID, this.categoryId, "select")));
        this.Controls.Add(new LiteralControl(string.Format("&nbsp;[<a href=\"javascript:{0}(this,'{1}')\" class=\"select\">{2}</a>]", clearDialog, this.ID, "clear")));
    }
    this.Controls.Add(new LiteralControl("</span>"));
}

protected virtual string getMediaDetails() {
    //...
    return String.Empty;
}

}

this is the code adding the validationcontrol the editcontrol is the instance of the control above

public override Control RenderValidationControl(Control editControl)
{
    Control ctrl = new PlaceHolder();

    RequiredFieldValidator req = new RequiredFieldValidator();
    req.ID = editControl.ClientID + "_validator";
    req.ControlToValidate = editControl.ID;
    req.Display = ValidatorDisplay.None;
    req.InitialValue = "0";
    req.EnableClientScript = false;
    req.ErrorMessage = "control cannot be blank";
    ctrl.Controls.Add(req);

    return ctrl;
}