c# - .net ViewState in page lifecycle

Question

I have a page containing a control called PhoneInfo.ascx. PhoneInfo is dynamically created using LoadControl() and then the initControl() function is called passing in an initialization object to set some initial textbox values within PhoneInfo.

The user then changes these values and hits a submit button on the page which is wired up to the "submit_click" event. This event invokes the GetPhone() function within PhoneInfo. The returned value has all of the new user entered values except that the phoneId value (stored in ViewState and NOT edited by the user) always comes back as null.

I believe that the viewstate is responsible for keeping track of user entered data across a postback, so I can't understand how the user values are coming back but not the explicitly set ViewState["PhoneId"] value! If I set the ViewState["PhoneId"] value in PhoneInfo's page_load event, it retrieves it correctly after the postback, but this isn't an option because I can only initialize that value when the page is ready to provide it.

I'm sure I am just messing up the page lifecycle somehow, any suggestion or questions would really help! I have included a much simplified version of the actual code below.

Containing page's codebehind

protected void Page_Load(object sender, EventArgs e)
{
    Phone phone = controlToBind as Phone;
    PhoneInfo phoneInfo = (PhoneInfo)LoadControl("phoneInfo.ascx"); //Create phoneInfo control
    phoneInfo.InitControl(phone); //use controlToBind to initialize the new control
    Controls.Add(phoneInfo);
}
protected void submit_click(object sender, EventArgs e)
{
    Phone phone = phoneInfo.GetPhone();
}

PhoneInfo.ascx codebehind

protected void Page_Load(object sender, EventArgs e)
{
}

public void InitControl(Phone phone)
{
    if (phone != null)
    {
        ViewState["PhoneId"] = phone.Id;
        txt_areaCode.Text = SafeConvert.ToString(phone.AreaCode);
        txt_number.Text =  SafeConvert.ToString(phone.Number);
        ddl_type.SelectedValue = SafeConvert.ToString((int)phone.Type);
    }
}

public Phone GetPhone()
{
    Phone phone = new Phone();
    if ((int)ViewState["PhoneId"] >= 0)
        phone.Id = (int)ViewState["PhoneId"];
        phone.AreaCode = SafeConvert.ToInt(txt_areaCode.Text);
        phone.Number = SafeConvert.ToInt(txt_number.Text);
        phone.Type = (PhoneType)Enum.ToObject(typeof(PhoneType),       SafeConvert.ToInt(ddl_type.SelectedValue));
        return phone;
    }
}

Answer 1

ViewState is managed between the Init and Load events. You should utilize code in or functions called from the Page_Init handler instead of Page_Load when you are concerned with maintaining values from postbacks.

See this link for more information on the ASP.NET page life cycle.

http://msdn.microsoft.com/en-us/library/ms178472.aspx