Question

I have three dropdowns for selecting a year inside a user control. On load I specify the selected value for one drop down. The other two drop downs are automatically getting assigned the same selected value. No matter which dropdown I assign a selected value to, they all three get the same selected value. I’ve tried recreating a new user control for the dropdowns but the same thing happens.

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="DropDownTest.ascx.cs" Inherits="WymanOrgManagement.DropDownTest" %>
<p>
    <asp:DropDownList ID="ddlStartDateYear" runat="server">
    </asp:DropDownList>
</p>
<p>
    <asp:DropDownList ID="ddlEndDateYear" runat="server">
    </asp:DropDownList>
</p>
<p>
    <asp:DropDownList ID="Year" runat="server"></asp:DropDownList>
</p>

Code Behind:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WymanOrgManagement
{
    public partial class DropDownTest : System.Web.UI.UserControl
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            populateDatesAndStates();
            ddlEndDateYear.SelectedIndex = 2;
        }

        protected void populateDatesAndStates()
        {
            ListItem init2 = new ListItem();
            init2.Text = init2.Value = "Year...";
            ddlStartDateYear.Items.Add(init2);
            ddlEndDateYear.Items.Add(init2);
            Year.Items.Add(init2);

            for (int i = DateTime.Now.Year - 1; i < DateTime.Now.Year + 10; i++)
            {
                ListItem item = new ListItem();
                item.Text = item.Value = i.ToString();
                ddlStartDateYear.Items.Add(item); ddlEndDateYear.Items.Add(item);
                Year.Items.Add(item);
            }
        }
    }
}

Can someone help me figure out why the three dropdowns seem to be in sync? Thanks!

Answer 1

All three dropdowns share the same instances of ListItem. When you set it to be Selected in one place, it becomes selected in all 3 places.

ListItem item = new ListItem();
item.Text = item.Value = i.ToString();
ddlStartDateYear.Items.Add(item); 
ddlEndDateYear.Items.Add(item);
Year.Items.Add(item);

What you probably want to do is this

ddlStartDateYear.Items.Add( i.ToString() ); 
ddlEndDateYear.Items.Add( i.ToString() );
Year.Items.Add( i.ToString() );

This will create a new instance of ListItem (with the same values) to go into each list.