Event not firing early enough in .NET Page cycle

Question

I have a Page (form) that has many UserControls on it, and I'm trying to have a single button to save everything. The UserControls are actually nested, so I wanted to somehow signal to each UC that it should save itself, instead of somehow wrapping everything into one event or having a single event trigger a cascade of save events.

My plan was to use a static class (props to this answer for the code):

public static class RequestScopedFormData
{
    private const string save_key = "request_form_is_saving";

    public static bool FormIsSaving
    {
        get
        {
            object o = HttpContext.Current.Items[save_key];
            return Convert.ToBoolean(o);
        }
        set
        {
            HttpContext.Current.Items[save_key] = value;
        }
    }
}

Ideally a button on my MasterPage would set RequestScopedFormData.FormIsSaving = true, and as .NET builds the Page and its UserControls, they would know to perform a save on themselves.

The problem I'm having is that I can't get an event to fire early enough in the Page lifecycle to save the UserControls. Even if I move the saving code to the PreRender event, and I move the save ImageButton to the Page itself (instead of the MasterPage), I cannot get the FormIsSaving set to true before the UC saving check.

It happens something like this:

• Page Page_Load
• MasterPage Page_Load
• UC Page_Loads and PreRenders (they are mixed, it prerenders some before it loads others)
• MasterPage SaveButton_Click event (this is where I set my class variable)
• MasterPage PreRender
• Page PreRender

So unfortunately the SaveButton_Click method happens AFTER the UCs are loaded, so they never save.

Answer 1

You can also check if postback was caused by the save button:

Request.Form["__EVENTTARGET"].Contains({YourSaveButton}.UniqueID)

The form variables are available earlier in the page life cycle.