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Question

dropdownlist selected index changed in asp.net using C#

Answer 1

+2 A:

You didn't call DataBind() after setting datasource.

protected void Ddl_SelectedIndexChanged(object sender, EventArgs e) {
    String sqlQuery="select SM.StateId,StateName From StateMast SM,CityMast CM where CM.StateId=SM.StateId AND CM.CItyId='"+ Convert.ToInt16(DdlCity.SelectedValue.ToString())+"'";

    DdlState.DataSource = cls.Select(sqlQuery);
    DdlState.DataTextField = "StateName";
    DdlState.DataValueField = "StateId";
    DdlState.DataBind();
}

EDIT (with validator):
ASPX:

<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="ddlCity" runat="server" AutoPostBack="true" 
            onselectedindexchanged="ddlCity_SelectedIndexChanged">
        </asp:DropDownList>
        <asp:RequiredFieldValidator ID="rfvCity" runat="server" ErrorMessage="City is required" ControlToValidate="ddlCity" InitialValue="0" Display="Dynamic"></asp:RequiredFieldValidator>
        <br />
        <asp:DropDownList ID="ddlState" runat="server" AutoPostBack="true">
        </asp:DropDownList>
        <asp:Button ID="Button1" runat="server" Text="Button" />
    </div>
    </form>
</body>

.cs:

public partial class ChildDDL : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Page.IsPostBack)
            return;

        ddlCity.Items.Add(new ListItem("Select One", "0"));
        ddlCity.Items.Add(new ListItem("City 1", "1"));
        ddlCity.Items.Add(new ListItem("City 2", "2"));
        ddlCity.Items.Add(new ListItem("City 3", "3"));

        List<State> lstState = new List<State>();
        lstState.Add(new State() { StateID = 1, StateName = "State 1", CityID = 1 });
        lstState.Add(new State() { StateID = 2, StateName = "State 2", CityID = 1 });
        lstState.Add(new State() { StateID = 3, StateName = "State 3", CityID = 1 });
        lstState.Add(new State() { StateID = 4, StateName = "State 4", CityID = 2 });
        lstState.Add(new State() { StateID = 5, StateName = "State 5", CityID = 2 });
        lstState.Add(new State() { StateID = 6, StateName = "State 6", CityID = 2 });
        lstState.Add(new State() { StateID = 7, StateName = "State 7", CityID = 3 });
        lstState.Add(new State() { StateID = 8, StateName = "State 8", CityID = 3 });

        Session["lstState"] = lstState;
    }

    protected void ddlCity_SelectedIndexChanged(object sender, EventArgs e)
    {
        List<State> lstState = (List<State>)Session["lstState"];

        ddlState.DataSource = lstState
            .Where(state => state.CityID == Convert.ToInt32(ddlCity.SelectedValue)); ;
        ddlState.DataTextField = "StateName";
        ddlState.DataValueField = "StateID";
        ddlState.DataBind();
    }

    public class State
    {
        public int StateID { get; set; }
        public string StateName { get; set; }
        public int CityID { get; set; }
    }
}

The page works well with validator.

Lee Sy En 2010-10-12 06:57:02

yaa i forgot... but now i added it... but its not working... what should i do?????????

Sheetal Inani 2010-10-12 07:10:24

the problem is that there are validators... so the function is not working.... means no post back occuring.. and no selected index change function call.....

Sheetal Inani 2010-10-12 07:14:53

what validator is that?

Lee Sy En 2010-10-12 07:30:25

this is personal information form... and i am using spry validatos.. i have created them in dreamweawer

Sheetal Inani 2010-10-12 07:42:20

I have modified my code with validator added. This is the best I can do.

Lee Sy En 2010-10-12 07:47:32

ok... thank you.. so much

Sheetal Inani 2010-10-12 07:52:37

Answer 2

A:

I think you have to update the update Panel in which the DropDowns are located...why aren't you using the AJAX Controls Toolkit Cascading DropDown? they are built for the same scenario as your.

http://www.asp.net/ajax/ajaxcontroltoolkit/samples/CascadingDropDown/CascadingDropDown.aspx

KhanZeeshan 2010-10-12 07:14:02

is there no way to do this without ajax

Sheetal Inani 2010-10-12 07:22:09

you can do a complete PostBack but its considered a bad practice.

KhanZeeshan 2010-10-12 07:23:35

how can i do complete post back??????? i have to submit my project on 2 o clock... so i have to do it with complete post back now... i will try ajax later

Sheetal Inani 2010-10-12 07:28:23

is function getting called?

KhanZeeshan 2010-10-12 07:33:56

no.... beacouse of validators the function is not caling

Sheetal Inani 2010-10-12 07:35:23

what should i do?????????

Sheetal Inani 2010-10-12 07:41:06

what type of validation are you performing?is it related to DropDown?

KhanZeeshan 2010-10-12 07:43:14

KhanZeeshan 2010-10-12 07:44:11

this is personal information form... and i am using spry validatos.. i have created them in dreamweawer... the validators are not related to dropdown list... but they are on the page....

Sheetal Inani 2010-10-12 07:48:26

its working without the validators

Sheetal Inani 2010-10-12 07:53:47

i'll suggest you use ASP.NET's own validators.

KhanZeeshan 2010-10-12 08:04:19

ok.... thank you

Sheetal Inani 2010-10-12 08:07:59

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dropdownlist selected index changed in asp.net using C#

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