Question

If I use QueryString to return the value of something stored in the URL and then populate a drop list with it that value like below:

industry = Request.QueryString["ind"].ToString();
industrydropdown.SelectedValue = industry;

category = Request.QueryString["cat"].ToString();
CatDropDown.SelectedValue = category

CatDropDown is filled automatically using code behind on SelectedIndexChanged with AutoPost Back enabled on industrydropdown.

    protected void industrydropdown_SelectedIndexChanged(object sender, EventArgs e)
    {
        string value = industrydropdown.SelectedValue;
        switch (value)
        {
            case "Ind1":
                CatDropDown.Items.Clear();
                CatDropDown.Items.Add("Categories for Ind1");
                break;

            case "Ind2":
                CatDropDown.Items.Clear();
                CatDropDown.Items.Add("Categories for Ind2");
                break;
        }

How would I go about filling my CatDropDownList from the QueryString when I am also using the on SelectedIndexChanged to fill the second drop down. Is this possible?

Answer 1

You can put the code in separate method of populating Category Dropdownlist. e.g.

industry = Request.QueryString["ind"].ToString();
industrydropdown.SelectedValue = industry;

fillCatDropDownList(); // Fill the category Dropdown before selection

category = Request.QueryString["cat"].ToString();
CatDropDown.SelectedValue = category

private void fillCatDropDownList()
{
string value = industrydropdown.SelectedValue;
    switch (value)
    {
        case "Ind1":
            CatDropDown.Items.Clear();
            CatDropDown.Items.Add("Categories for Ind1");
            break;

        case "Ind2":
            CatDropDown.Items.Clear();
            CatDropDown.Items.Add("Categories for Ind2");
            break;
    }
 }

and then

protected void industrydropdown_SelectedIndexChanged(object sender, EventArgs e)
{
  fillCatDropDownList();
}