Bind a gridview on SelectedIndexChanged Event using AJAX

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C#

ASP.NET

Ajax

I want to Bind my Gridview on Selected Index change.. I dont know why am i stuck in this simple issue.. My Code:

protected void DropDownListHostelRoom_SelectedIndexChanged(object sender, EventArgs e)
           {
               if (DropDownListHostelRoom.SelectedValue == "Single")
               {
                   SqlConnection cn = new SqlConnection(@"Data Source=.;Initial Catalog=_uniManagement;Integrated Security=True");
                   string sql = "select HRName,Booked,_Issued from _hostel_room where booked = 'NO' and _issued = 'NO' and _hrtypid = 1";
                   SqlCommand cmd = new SqlCommand(sql, cn);
                   SqlDataAdapter da = new SqlDataAdapter(cmd);
                   DataTable dt = new DataTable();
                   da.Fill(dt);
                   GridViewHostelRoom.DataSource = dt;
                   GridViewHostelRoom.DataBind();
                   UpdatePanel1.DataBind();

               }
   }

<pre lang="xml"><asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
    <asp:ScriptManager ID="ScriptManagerMemberType" runat="server">
    </asp:ScriptManager>
    <asp:UpdatePanel ID="UpdatePanelMemberType" runat="server">
        <ContentTemplate>
            <div>
                <fieldset>
                    <legend>Create Hostel Member</legend>
                    <asp:Label ID="LabelMemberType" runat="server" Text="Member Type"></asp:Label>&nbsp
                    <asp:DropDownList ID="DropDownListMemberType" AutoPostBack="true" runat="server"
                        DataTextField="HMemTypeName" DataValueField="_HMemTypeID" OnSelectedIndexChanged="DropDownListMemberType_SelectedIndexChanged">
                    </asp:DropDownList>
                    <br />
                    <asp:Label ID="LabelMemberName" runat="server" Text="Search"></asp:Label>
                    <asp:TextBox ID="TextBoxMemberName" runat="server" OnTextChanged="TextBoxMemberName_TextChanged"></asp:TextBox><br />
                    <asp:GridView ID="GridViewMemberType" runat="server" AutoGenerateColumns="False"
                        Style="margin-right: 0px" DataKeyNames="_PersID">
                        <Columns>
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:CheckBox ID="CheckBoxMemberType" runat="server" OnCheckedChanged="CheckBoxMemberType_CheckedChanged" />
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:BoundField DataField="FirstName" />
                            <asp:BoundField DataField="LastName" />
                            <asp:BoundField DataField="DOB" />
                            <asp:BoundField DataField="FatherName" />
                            <asp:BoundField DataField="Nationality" />
                        </Columns>
                    </asp:GridView>
                    <asp:Button ID="ButtonHostelMember" runat="server" Text="Create Hostel Member" OnClick="ButtonHostelMember_Click" />
                    <asp:Label ID="LabelTemporaryID" runat="server" Text=""></asp:Label>
                </fieldset>
            </div>
        </ContentTemplate>
    </asp:UpdatePanel>
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
            <div>
                <fieldset>
                    <legend>Hostel Details </legend>
                    <asp:Label ID="LabelHostelRoomType" runat="server" Text="Room Type"></asp:Label>
                    <asp:DropDownList ID="DropDownListHostelRoom" runat="server" DataTextField="HTypeName"
                        DataValueField="_HRTypID" OnSelectedIndexChanged="DropDownListHostelRoom_SelectedIndexChanged">
                    </asp:DropDownList>
                    <asp:GridView ID="GridViewHostelRoom" runat="server">
                        <Columns>
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:LinkButton ID="LinkButtonRoomIssue" runat="server">Click To Issue</asp:LinkButton>
                                </ItemTemplate>
                            </asp:TemplateField>
                        </Columns>
                    </asp:GridView>
                </fieldset>
            </div>
        </ContentTemplate>
    </asp:UpdatePanel>
</asp:Content>