dropdownlist error in c# code

Question

i want to show a value in DropDownList at page load and the value is "1 Year". here is my Database Table

id  instal
0   Choose
6   6 Month
12  1 Year
24  2 Year
36  3 Year

here is my ASPX code:

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3" %>

<asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" Runat="Server">
    <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" 
        DataSourceID="SqlDataSource1" DataTextField="instal" DataValueField="id" 
        onselectedindexchanged="DropDownList1_SelectedIndexChanged">
    </asp:DropDownList>
    <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
        ConnectionString="<%$ ConnectionStrings:paconn %>" 
        SelectCommand="SELECT * FROM [cms_instal] ORDER BY [id]">
    </asp:SqlDataSource>
</asp:Content>

and its my C# code:

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Collections;
using System.Web.SessionState;

public partial class Default3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        DropDownList1.Text = "1 Year";
    }
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {

    }
}

but problem is that when my page is loaded it gives an error "'DropDownList1' has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value"

i am using ASP.Net C#, SQL Server 2008.

possible duplicate of How to SELECT a dropdown list item by value programatically — Austinh100
– Austinh100, Commented Jun 24, 2014 at 19:26
you can try this DropDownList1.SelectedItem.Text = "1 Year"; — Karthik Ganesan
– Karthik Ganesan, Commented Jun 24, 2014 at 19:29

j.f. · Accepted Answer · 2014-06-24 20:42:53Z

1

The text property of a DropDownList gets or sets the SelectedValue. Since your DataValueField is set to "id", you would need to set the Text property to "12".

edited Jun 24, 2014 at 20:42

answered Jun 24, 2014 at 19:30

j.f.

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Comments

rene · Accepted Answer · 2014-06-24 20:37:38Z

0

Move the text to the LoadComplete event

    void Page_LoadComplete(object sender, EventArgs e)
    {
        DropDownList1.Text = "1 Year"; 
    }

The list binding has not occurred in page load so the list is not able to take another value which is not in the list. Setting the value after page load will allow it to use an existing value.

edited Jun 24, 2014 at 20:37

rene

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answered Jun 24, 2014 at 19:27

Avneesh

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1 Comment

Avneesh Over a year ago

You need to set the value after load event or after the control has binded properly as the list binding has not completed. So it needs to load up the values from the datasoure to allow it set a value from the list. msdn.microsoft.com/en-us/library/…

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