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I placed an dropdown list in an update panel

asp:UpdatePanel ID="UpdatePanel3" runat="server">
                                    <asp:DropDownList ID="DropDownList1" runat="server" Height="24px" 


and in formload i write like this

protected void Page_Load(object sender, EventArgs e)
            if (!IsPostBack)
                connStr = ConfigurationManager.ConnectionStrings["NFTRANSConnectionString1"].ConnectionString;

  public void Driverjobcodeload()

            DataTable dt = new DataTable();
            SqlConnection con = new SqlConnection(connStr);
            SqlDataReader ddDR = null;
            SqlCommand cmd = new SqlCommand("Select DriverCode ,Driverid from DriverMaster_tbl ", con);
            ddDR = cmd.ExecuteReader();
            DropDownList1.DataSource = dt;
            DropDownList1.DataTextField = "DriverCode";
            DropDownList1.DataValueField = "Driverid";

but when i run this in browser Iam not able to select any item in the dropdownlist once i expan the list it get shrinked automatically within a second and even if i manage to select one its willnot be the selected item selected item will be default the first one.

I know since iam a new bie to web development it may be a error from my side but can anyone suggest any possible issue
Updated 20-Feb-13 1:28am
ali_heidari_ 20-Feb-13 5:42am
your dropdown list not in update panel ! and and set updatemode of update panel to always ! UpdateMode="Always" ... hope help you
SREENATH GANGA 20-Feb-13 6:07am
thank you ....but vwhen i try to put it inside iam getting error at run at server Parser Error Message: Type 'System.Web.UI.UpdatePanel' does not have a public property named 'DropDownList'.
ali_heidari_ 20-Feb-13 6:10am
you cant put it into it directly! updatepanel has a member named ContentTemplate! you should put dropdownlist on ContentTemplate
SREENATH GANGA 20-Feb-13 6:30am
Thankyou for your support I kept the dropdownlist inside contenttemplate still issue continues
ali_heidari_ 20-Feb-13 6:39am
when you use updatepanel and ajax, your dropdownlist will reload with any event!and when you click on dropdownlist ,page will reload and dropdownlist closed! so i suggest you keep dropdownlist out of updatepanel and make a trigger for it if you want any event raise(like OnSelectedIndexChanged!

Here's jQuery based example. it takes all keyboard and mouse events into account, especially clicks:

if (!$.support.leadingWhitespace) { // if IE6/7/8
        .bind('focus mouseover', function() { $(this).addClass('expand').removeClass('clicked'); })
        .bind('click', function() { $(this).toggleClass('clicked'); })
        .bind('mouseout', function() { if (!$(this).hasClass('clicked')) { $(this).removeClass('expand'); }})
        .bind('blur', function() { $(this).removeClass('expand clicked'); });
Use it in combination with this piece of CSS:
select {
    width: 150px; /* Or whatever width you want. */
select.expand {
    width: auto;
All you need to do is to add the class wide to the dropdown element(s) in question.
<select class="wide">

You can take dropdownlist in to trigger tag in update panel.
I just follow your code. My markup is

<form id="form1" runat="server">
<asp:scriptmanager runat="server" id="scrManager" enablepartialrendering="true" xmlns:asp="#unknown"></asp:scriptmanager>
    <asp:updatepanel id="UpdatePanel3" runat="server" xmlns:asp="#unknown">

                              <asp:dropdownlist id="DropDownList1" runat="server" height="24px" xmlns:asp="#unknown">
                                   onselectedindexchanged="DropDownList1_SelectedIndexChanged" Width="186px" AutoPostBack="true">

My codebehind is
protected void Page_Load(object sender, EventArgs e)
    if (!IsPostBack)
public void Driverjobcodeload()
    var dt = new DataTable();
    dt.Columns.Add("DriverCode", typeof(string));
    dt.Columns.Add("Driverid", typeof(string));

    DataRow row1 = dt.NewRow();
    row1["DriverCode"] = "1";
    row1["Driverid"] = "One";
    DataRow row2 = dt.NewRow();
    row2["DriverCode"] = "2";
    row2["Driverid"] = "Two";
    DataRow row3 = dt.NewRow();
    row3["DriverCode"] = "3";
    row3["Driverid"] = "Three";
    DropDownList1.DataSource = dt;
    DropDownList1.DataTextField = "DriverCode";
    DropDownList1.DataValueField = "Driverid";
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    var z = 100;

The code is working fine. Please check that and compare with your code. Let me know any difference it with your code except database access.
SREENATH GANGA 20-Feb-13 6:05am
hy script manager is at masterpage
S. M. Ahasan Habib 20-Feb-13 6:14am
That will not create any problem. Anything else you found?
SREENATH GANGA 20-Feb-13 6:34am
Your code is fine. The problem is with the HTML markup. As you have not posted the complete markup, here is what i assume you have missed:
1. A ScriptManager on your aspx page.
2. DropDownList tag is not well formed.
3. UpdatePanel's UpdateMode property is not specified, so by default it is "Always".

Replace your markup with the following and try:
<asp:scriptmanager runat="server" id="ScriptManager1"></asp:scriptmanager>
<asp:updatepanel id="UpdatePanel3" runat="server" updatemode="Conditional"/><contenttemplate>
<asp:DropDownList ID="DropDownList1" runat="server"></DropDownList>

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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