Question

I have a web user control that holds three dropdownlists: One holds days, second holds months and the third one holds years. Days and months are static.But year items will change upon need to avoid entering wrong year. Let me first list here what I do in order, then i’ll ask my question:

1. I have a private int yearSpan.

2. In private method PopulateYearList I say:

   int year = DateTime.Now.Year;
   int span = year - this.yearSpan;
   for (int i = span; i <= year; i++)
   {
       ddlYears.Items.Add(i.ToString());//Here I get NullReferenceException
   }
   

3. I’ve overriden the default constructor to receive yearSpan as an argument:

    public DatePicker(int yearSpan)
    {
       this.yearSpan = yearSpan;
       this.PopulateYearList();
    }
   

Now, as you might have guessed in my PopulateYearList method I get NullReferenceException because I try to add an item to ddlYears that has not been constructed yet. What would you suggest to do to solve this?

Answer 1

Ether call the PopulateYearList in the Page_Load of your usercontrol. Like this:

protected void Page_Load(object objSrc, EventArgs e)
{
    if(this.IsPostBack)
      PopulateYearList()
}

Or make the PopulateYearList public and call it on the page when you bind the page controls