How do I keep my items in asp:dropdownlist after !Page.IsPostBack?

Question

I am loading a list of value/text into a asp:dropdownlist by calling a stored procedure. I populate the dropdownlist on the PageLoad method inside a.Page:IsPostBack block like so:

if (!Page.IsPostBack)
{
     GetDropDownLists();
     DataBind();
}

And this is my code implementation for the backend:

protected void GetDropDownLists()
{
     DataTable dt = new DataTable();

     SqlConnection conn = new SqlConnection(connString);
     SqlCommand cmd = new SqlCommand("get_articletype", conn);
     cmd.CommandType = CommandType.StoredProcedure;
     SqlDataAdapter adapter = new SqlDataAdapter(cmd);
               
     adapter.Fill(dt);
     xArticleTypeList.Items.Clear();
     xArticleTypeList.Items.Insert(0, new ListItem("- Select.. -", "0"));
     xArticleTypeList.SelectedIndex = 0;
     xArticleTypeList.DataSource = dt;
     xArticleTypeList.DataValueField = "TypeValue";
     xArticleTypeList.DataTextField = "TypeName";
     xArticleTypeList.DataBind();
}

If my code isn't inside a.Page,IsPostBack block. after I click my save button the default value will always be the first item of the dropdownlist. But once I put my code inside the.Page:IsPostBack block my dropdownlist is empty. For reference here is the frontend implementation of my asp:dropdownlist.

<asp:DropDownList ID="xArticleTypeList" EnableViewState="true" AutoPostBack="true" CssClass="form-control" runat="server" />

I understand that there are other topics that cover this question, but none of the proposed solutions worked for me. Thanks you in advance for your inputs.

Answer 1

Your problem is that you inserting the blank please select row BEFORE you bind. As a result, when you bind, you are blowing out the drop down.

Try it this way:

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


    void LoadData()
    {
        using (SqlConnection conn = new SqlConnection(Properties.Settings.Default.TEST4))
        {
            using (SqlCommand cmd = new SqlCommand("get_articletype", conn))
            {
                DataTable dt = new DataTable();
                cmd.CommandType = CommandType.StoredProcedure;
                conn.Open();
                dt.Load(cmd.ExecuteReader());

                xArticleTypeList.DataSource = dt;
                xArticleTypeList.DataValueField = "TypeValue";
                xArticleTypeList.DataTextField = "TypeName";
                xArticleTypeList.DataBind();

                xArticleTypeList.Items.Insert(0, new ListItem("- Select.. -", "0"));
            }
        }
    }

And GET RID of your extra call re-bind You have this:

 GetDropDownLists();
 DataBind();   <--- remove unless you need, or execute BEFORE the GetDropDownList()

So move your add/insert blank row to the drop down to AFTER the drop down data bind.

And REMOVE your DataBind() - you don't need it, and if for some reason you do, then move the DataBind() to before your load of the GetDropDownLists() - but my guess is that you just tossed that in the hope of making this work, and it going to cause the combo box to re-select - so remove unless you give a REALL GOOD HIGH quality outline and narrative as to why you have the DataBin() command there - (but as as noted, if you really, but really really do need to execute that DataBind() command - move it to before the load of the combo).

So, add the blank row after