Question

I have two dropdown ddlCountry and ddlState and one button Submit.
While ddlstate is in update panel.
On submit of button value of both dropdown store in database.
And I show the data in Repeater Control.(In HTML Table structure)
ASPX CODE

<table id="tablelist" class="csstablelist" cellspacing="1" cellpadding="1">
                    <tr>
                        <td class="csstablelisttoptr">
                            ddlCountryID
                        </td>
                        <td class="csstablelisttoptr">
                            ddlCountryText
                        </td>
                        <td class="csstablelisttoptr">
                            ddlstateText
                        </td>
                    </tr>
                    <asp:Repeater ID="repeaterList" runat="server" OnItemDataBound="repeaterList_ItemDataBound">
                        <ItemTemplate>
                            <tr onclick="selectRow(this);">
                                <td class="csstablelisttd" style="display: none">
                                    <asp:Label ID="ddlCountryID" runat="server" Text='<%#Eval("ddlCountryID")%>'></asp:Label>
                                </td>
                                <td class="csstablelisttd">
                                    <asp:Label ID="ddlCountryText" runat="server" Text='<%#Eval("ddlCountryText")%>'></asp:Label>
                                </td>
                                <td class="csstablelisttd">
                                    <asp:Label ID="ddlstateText" runat="server" Text='<%#Eval("ddlstateText")%>'></asp:Label>
                                </td>
                            </tr>
                        </ItemTemplate>
                    </asp:Repeater>
                </table>
<asp:DropDownList ID="ddlCountry" runat="server" CssClass="csstextbox" Width="207px" AutoPostBack="true" OnSelectedIndexChanged="ddlCountry_SelectedIndexChanged">
</asp:DropDownList>
<asp:UpdatePanel ID="updatePanelState" runat="server">
    <ContentTemplate>
        <asp:DropDownList ID="ddlState " runat="server" CssClass="csstextbox" Width="177px">
        </asp:DropDownList>
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="ddlCountry" EventName="SelectedIndexChanged" />
    </Triggers>
</asp:UpdatePanel>
<asp:Button ID="btnSave" runat="server" Width="80px" OnClientClick="return validateForm();" Text="Save" CssClass="cssbutton" OnClick="btnSave_Click" />


ddlCountryID | ddlCountryText | ddlstateText
1            | USA            | XYZ
2            |India           | PQR

Onclick of TR i write below (SelectRow(this)) function in javascript for highliting the repeater value and dropdown value match and getting selected.

<script type="text/javascript">
function selectRow(objTR)
{
 var ddlCountry =document.getElementById('<%=ddlCountry.ClientID %>');
 var ddlState =document.getElementById('<%=ddlState .ClientID %>');

    for (i = 0; i < ddlCountry .options.length; i++)
    {
        if (ddlCountry .options[i].text == objTR.cells[1].innerText.trim())
            break;
    }           
    ddlCountry .options[i].selected = true;

    __doPostBack(ddlCountry .id, objTR.cells[2].innerText.trim());    
}
</script>

I write ddlCountry SelectedIndexChangedEvent In code behind.

From Javascript I am firing __doPostBack() and passing ddlCountry as event target ddlStateText as event argument to SelectedIndexChangedEvent and getting value in event like this.

string stateDescription = Request["__EVENTARGUMENT"];
ddlState .Items.FindByText(stateDescription ).Selected = true;//for highliting the repeater value and dropdown value match and selected

Binding Country on pageLoad

 if(!Ispostback)
protected Void BindCountry()

{

strSQL = @"SELECT countryID,Country from Country_Master";
        DataTable dataTableCountry = null;
        dataTableCountry = objSqlDbComm.ExecuteDatasetQuery(strSQL).Tables[0];

        int countryID;
                string Country;     
        var dictioneryCountry = new Dictionary<int, string>();
        foreach(DataRow dr in dataTableCountry.Rows)
        {
            countryID = Convert.ToInt32(dr["countryID"]);
            Country= dr["Country"].ToString();          
            dictioneryCountry.Add(countryID,Country);
        }
        ddlCountry.Items.Clear();
        ddlCountry.DataTextField = "Value";
        ddlCountry.DataValueField = "Key";
        ddlCountry.DataSource = dictioneryCountry;
        ddlCountry.DataBind();
        ddlCountry.Items.Insert(0, new ListItem("[Select]", "-1"));
        ddlCountry.Items[0].Selected = true;
}

My problem is if I have following repeater data.

ddlCountryID | ddlCountryText | ddlstateText
1            | USA            | XYZ
2            |India           | PQR
2            |India           | MNO

When I select row number 3 that have country india and state mno then __dopostback() method is fire.

When I goes to row number 1 then __dopostback() method is fire.

When I come from row nuber 1 to 3 then method is fire correct way but when goes from row nuber 3 to 2 having country id same __dopostback() method is not fire and state is not selected from ddlstate.

Answer 1

If you debug your code, you will see that __doPostBack() is indeed working because the code in Page_Load is being executed (try setting a breakpoint here to check). The issue is that the index of your DropDownList is not changing, therefore the IndexChanged event is not fired and ddlCountry_SelectedIndexChanged never runs. When you call __doPostBack(), this not the same as manually calling ddlCountry_SelectedIndexChanged from the codebehind.

Is there a particular reason that you would be doing a post back other than to set this dropdown list value?

SOLUTION 1

I would advise removing the __doPostBack() line and adding the following instead:

var state = objTR.cells[2].innerText.trim();
for (var i = 0; i < ddlState.options.length; i++)
{
    if (ddlState.options[i].text == state)
    {
        ddlState.options[i].selected = true;
        break;
    }
}

SOLUTION 2

Alternatively, if you really have to post back, you could do the following:

a. Add a hidden button inside of your update panel like this:

<div style="display: none">
<asp:Button ID="btnState" OnClick="btnState_Click" runat="server" />
</div>

b. Change your javascript to do the following after selecting the country:

document.getElementById('__EVENTARGUMENT').value = objTR.cells[2].innerText.trim();
document.getElementById('<%= btnState.ClientID %>').click();

c. Create a FilterState() function and call this from your ddlcountry indexchanged event

protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
{
    FilterState();
}

private void FilterState()
{
// insert whatever filtering code you had here
}

d. Add your btnState_Click function (note that the way you were setting the selected item of ddlState before would throw an error if an item was already selected.):

protected void btnState_Click(object sender, EventArgs e)
{
    FilterState();
    string state = Request["__EVENTARGUMENT"];
    if (state != "")
        ddlState.SelectedValue = state;
}

SOLUTION 3

A third solution would allow you to still use __doPostBack, and scrap the SelectedIndexChanged event altogether by putting this in the Page_Load function:

if (IsPostBack && Request["__EVENTTARGET"] == ddlCountry.UniqueID)
{
    FilterState();
    string stateDescription = Request["__EVENTARGUMENT"];
    if (stateDescription != "")
        ddlState.SelectedValue = stateDescription;
}

On another note, for your BindCountry function there’s no real reason to use a Dictionary, you can just bind the DataTable directly:

strSQL = @"SELECT countryID,Country from Country_Master";
DataTable dataTableCountry = objSqlDbComm.ExecuteDatasetQuery(strSQL).Tables[0];
ddlCountry.Items.Clear();
ddlCountry.DataSource = dataTableCountry;
ddlCountry.DataTextField = "Country";
ddlCountry.DataValueField = "countryID";
ddlCountry.DataBind();
ddlCountry.Items.Insert(0, new ListItem("[Select]", "-1"));
ddlCountry.Items[0].Selected = true;