Question

I have a custom control that mimics to some extent the built in ASP.Net CheckboxList control. On the render event I generate a UL>LI>Checkbox#customId structure based on the DataSource the control is getting.

My biggest puzzle is that, even though the input HTML elements get rendered on the page, when submitting back the page, the Request.Form collection has no data related to these inputs.

So, my question is this:
Once a PostBack is triggered, is there a way to get the inputs checked by the user?

Thanks in advance,
Kali

Answer 1

Typically, a custom server control will implement the SaveViewState, LoadViewState, and TrackViewState methods to manage the state of controls.

I don’t know how you’re control is built so I can’t give you the exact code, but here’s an example of those methods being used in a control that I created:

protected override void LoadViewState(object savedState)
{
    if (savedState != null)
    {
        object[] state = (object[])savedState;

        if (state[0] != null)
            base.LoadViewState(state[0]);
        if (state[1] != null)
            ((IStateManager)ItemStyle).LoadViewState(state[1]);
        if (state[2] != null)
            ((IStateManager)headerStyle).LoadViewState(state[2]);
        if (state[3] != null)
            ((IStateManager)AlternatingItemStyle).LoadViewState(state[3]);
    }
}

protected override object SaveViewState()
{
    object[] state = new object[4];

    state[0] = base.SaveViewState();
    state[1] = itemStyle != null ? ((IStateManager)itemStyle).SaveViewState() : null;
    state[2] = headerStyle != null ? ((IStateManager)headerStyle).SaveViewState() : null;
    state[3] = alternatingItemStyle != null ? ((IStateManager)alternatingItemStyle).SaveViewState() : null;

    return state;
}

protected override void TrackViewState()
{
    base.TrackViewState();

    if (itemStyle != null)
        ((IStateManager)itemStyle).TrackViewState();
    if (headerStyle != null)
        ((IStateManager)headerStyle).TrackViewState();
    if (alternatingItemStyle != null)
        ((IStateManager)alternatingItemStyle).TrackViewState();
}

Aside from the above methods, if you want to reload information from the Request object, you can implement the IPostBackDataHandler interface, which requires these two methods:

public virtual bool LoadPostData(string postDataKey, NameValueCollection postCollection)
{
    string somePostedValue = postCollection["SomePostedValue"];
    string anotherPostedValue = postCollection["AnotherPostedValue"];
}

public virtual void RaisePostDataChangedEvent()
{

}