ASP.Net - How do I add a HiddenField from another WebControl and maintain it?

Question

I've got a WebControl that I want to dynamically add a HiddenField from.

I've tried the following example: Click here, but that doesn't work due to the fact this.Page.Form is null in the Page Init event.

I've tried the following, but the value is never maintained:

HiddenField hd_IsDirty = new HiddenField();

protected override void OnInit(EventArgs e)
{

    this.Controls.Add(hd_IsDirty);
    hd_IsDirty.ID = "hd_IsDirty";

    base.OnInit(e);

}

Answer 1

See this answer on this question.

The answer will show you how to add a control dynamically, which is what you are trying to do.

Answer 2

The following works:

Create the control every time (seems bad!):

HiddenField hd_IsDirty = new HiddenField();

Tell the Page that the control requires a ControlState OnInit:

    this.Page.RegisterRequiresControlState(this);

Override the ControlState methods:

protected override object SaveControlState()
{

    object obj = base.SaveControlState();

    if (!string.IsNullOrEmpty(hd_IsDirty.Value))
    {
        if (obj != null)
        {
            return new Pair(obj, hd_IsDirty.Value);
        }
        else
        {
            return hd_IsDirty.Value;
        }
    }
    else
    {
        return obj;
    }
}

protected override void LoadControlState(object state)
{
    if (state != null)
    {
        Pair p = state as Pair;
        if (p != null)
        {
            base.LoadControlState(p.First);
            hd_IsDirty.Value = (string)p.Second;
        }
        else
        {
            if (state is string)
            {
                hd_IsDirty.Value = (string)state;
            }
            else
            {
                base.LoadControlState(state);
            }
        }
    }
}

Answer 3

Theres always the dynamic controls placeholder at - http://www.denisbauer.com/ASPNETControls/DynamicControlsPlaceholder.aspx