Why is the dropdownlist in my web part losing the values?

Hi,

I've been trying to add two dropdown lists and a button to a web part. I want to pass the values a user selects in the dropdowns to a filter on that web part.

However, when the values are submitted (either with a button click on a SelectedIndexChanged event, the page posts, but the values are lost.)

In an effort to test, I'm just tyring to write the passed values to the page, but they always return null. If I use an IsPostback event in the CreateChildControls method, the dropdownlists lose all of their values (though from what I've read, I thought they should keep them)?

I'm sure I'm missing something on how ViewState works with SharePoint. Any help is greatly appreciated. (Code snippet below.)

Thanks!

Sami


        public void CreateDDLsAndButtons()
        {
            try
            {
                ddlOption1.ID = "ddlOption1";
                ddlOption2.ID = "ddlOption2";

                ListItem liTitle = new ListItem();
                liTitle.Value = "Title";
                liTitle.Text = "Title";
                ddlOption1.Items.Add(liTitle);
                ddlOption2.Items.Add(liTitle);

                ListItem liStudent = new ListItem();
                liStudent.Value = "Author";
                liStudent.Text = "Student";
                ddlOption1.Items.Add(liStudent);
                ddlOption2.Items.Add(liStudent);

               //If I disable the AutoPostBack, the SelectedIndexChanged doesn't get called, though I'm not sure it's getting called when this is enabled, although the page does post back.
                ddlOption1.AutoPostBack = true;
                ddlOption2.AutoPostBack = true;
               
                ddlOption1.SelectedIndexChanged += new System.EventHandler(this.ddlOption1_SelectedIndexChanged);
                ddlOption2.SelectedIndexChanged += new System.EventHandler(this.ddlOption2_SelectedIndexChanged);

                btnSubmit.ID = "btnSubmit";
                btnSubmit.Text = "Go";
                btnSubmit.Click += new System.EventHandler(this.btnSubmit_Click);
               
            }
            catch (Exception ex)
            {
                WriteToEventLog(ex.ToString(), "Multigenre Research", EventLogEntryType.Error, "Application");
            }
           
        }

        protected override void CreateChildControls()
        {
            base.CreateChildControls();
           
                CreateDDLsAndButtons();
           
            this.Controls.Add(ddlOption1);
            this.Controls.Add(ddlOption2);
            this.Controls.Add(btnSubmit);
            FunctiontoUseTheValues(sOption1, sOption2);
           
        }
        private void ddlOption1_SelectedIndexChanged(object sender, System.EventArgs e)
        {
           //I've tried putting this in a session var as well and no luck.
            sOption1 = ddlOption1.SelectedItem.Value;
            HttpContext.Current.Response.Write("<br />1: " + HttpContext.Current.Session["sOption1"]);
        }

        private void ddlOption2_SelectedIndexChanged(object sender, System.EventArgs e)
        {
            sOption2 = ddlOption2.SelectedItem.Value;
            HttpContext.Current.Response.Write("<br />2: " + HttpContext.Current.Session["sOption2"]);
        }

        private void btnSubmit_Click(object sender, System.EventArgs e)
        {
            sOption1 = ddlOption1.SelectedItem.Value;
            HttpContext.Current.Response.Write("<br />Option 1 value: " + sOption1);
           
        }Start Free Trial