Page Cycles - Right way to input data to database

I have a page that has a f开发者_StackOverflow社区ew textboxes and a dropdownlist. When a logged in user opens this page the boxes are filled with data that he has input before, he can change the data and update it by pushing a update button. There is also that dropdownlist which has a dynamically populated data for him to choose from.

What is the best way to make this page work. Where in the page cycles do I populate the forms and where do I input the data to the datatable.

At the moment I'm populating the data on PreRender but the dropdownlist on the preinit. I have a button event handler to do the update on the datatable. The problem is that the autopostback messes up the data in the dropdownlist because its dynamically populated, how would I go by fixing this?

Here is what I follow in most of my cases

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        InitDropdDownListes();
        LoadDataFromDataBase();
    }

}

void InitDropdDownListes()
{
    // fill drop down boxes

}

void LoadDataFromDataBase()
{
    // load from database

}

protected void OnDropdownListChanges(object sender, EventArgs e)
{
    // reload the new data from database
    LoadDataFromDataBase();
}


protected void btnSave_Click(object sender, EventArgs e)
{
    // Save to database

}