__doPostBack() is not working when having ID(__EvenTarget) is same

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ASP.NET

Javascript

.NET

Ajax

I have two dropdown ddlCountry and ddlState and one button Submit.

While ddlstate is in update panelwhile 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.

<pre lang="Javascript">function selectRow(objTR)
{
    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());    
}

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

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.