如何动态填充使用数据表嵌套在表单视图中的下拉列表？

Question

I am trying to fill a asp:DropDownList with data from SQL and with the use of a datatable. However I get the error 'CreatedByDropList' has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value

The asp:DropDownList is inside of a formview whos select is populated by a gridview.

here is the HTML for the DropList control in Edit and Insert template of the Formview:

<asp:DropDownList ID="CreatedByDropList" AppendDataBoundItems="true" SelectedValue='<%# Bind("CreatedBy") %>' runat="server" />

Here is the Code Behind:

protected void FormView1_DataBound(object sender, EventArgs e)
{
    if (FormView1.CurrentMode == FormViewMode.Insert)
    {
        DropDownList ddlCreatedBy = FormView1.FindControl("CreatedByDropList") as DropDownList; //Placed BreakPoint Here

        using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["MySqlServer"].ConnectionString))
        {
            SqlCommand cmd = new SqlCommand(@"SELECT RLS.RoleName [RoleName], URS.UserID [UserID], USRS.UserName[UserName], USRS.FirstName[FirstName], USRS.LastName[LastName]
                                                FROM [Roles] RLS Inner JOIN [Users] USRS LEFT JOIN [UserRoles] URS 
                                                ON USRS.[UserID] = URS.[UserID] ON RLS.[RoleID] = URS.[RoleID] 
                                                WHERE RLS.[RoleName] = 'Blog Editors'",conn);
            conn.Open();
            using (SqlDataReader reader1 = cmd.ExecuteReader())
            {
                while (reader1.Read())
                {
                    int numUserID = reader1.GetInt32(1);
                    string strFirstName = reader1.GetString(3);
                    string strLastName = reader1.GetString(4);
                    string newUserName = strFirstName + " " + strLastName;
                }

                    SqlDataAdapter da = new SqlDataAdapter(cmd);
                    DataTable dt = new DataTable();
                    da.Fill(dt);
                    ddlCreatedBy.DataSource = dt;
                    ddlCreatedBy.DataTextField = "newUserName";//Placed BreakPoint Here
                    ddlCreatedBy.DataValueField = "numUserID";//Placed BreakPoint Here
                    ddlCreatedBy.DataBind();
            }



        }

}

I placed Breakpoints throughout for some troubleshooting but the debug window stays blank(meaning all debug windows are blank and useless) the entire time.

Answer 1

reader 1 isn't doing anything. It's just iterating over all of the rows returned from the command, assigning them to variables, then not doing anything with them, as far as this snippet shows.

Also, you don't have any columns in your DataTable named "newUserName" or "numUserId". Change the last 4 lines to this:

foreach(DataRow row in dt.Rows)
{
    ddlCreatedBy.Items.Add(new ListItem(row["FirstName"] + " " + row["LastName"], row["UserId"]);
}