Populating Gridview with dropdownlist and checkboxes

<table>
           <tr><td><asp:Label ID="lblFmlDate" runat="server" Text="Date"></asp:Label></td>
                <td><asp:TextBox ID="txtFmlDate"  runat="server" Enabled ="False"></asp:TextBox>
                    <asp:ImageButton ID="imgBtnFmlDate" ImageUrl="~/Images/Calendar_scheduleHS.png" runat="server" />
                    <AjaxToolkit:CalendarExtender ID="calExtrFmlDate"
                        OnClientDateSelectionChanged ="checkDate" runat="server"
                        TargetControlID="txtFmlDate" PopupButtonID="imgBtnFmlDate" Enabled="True">
                    </AjaxToolkit:CalendarExtender>
            </td></tr>
            <tr>
            <td><asp:Label ID="lblDisease" runat="server" Text="Disease"></asp:Label></td>
            <td><asp:TextBox ID="txtDisease" Enabled ="False" runat="server" ></asp:TextBox></td>
            <td><asp:Button ID="cmdDiseaseAdd" Enabled ="False" runat="server" Text="Add"
                    width="60px" onclick="cmdDiseaseAdd_Click" ValidationGroup="B"/></td>
            <td><asp:Button ID="cmdDiseaseDel" Enabled ="False" runat="server" Text="Delete"
                    width="60px" onclick="cmdDiseaseDel_Click"/></td>
            </tr><tr>

grid view 
            <td colspan="6">
            <asp:GridView ID="grdFmlHist" runat="server" AllowPaging="True" Enabled ="False"
            AutoGenerateColumns="False" DataKeyNames="Relationship" Height="40px" WIDTH="450px"
            PageSize="8" ShowFooter="True"  onrowdatabound="grdFmlHist_RowDataBound" >
            <PagerSettings Mode="NumericFirstLast" />
            <RowStyle BackColor="WhiteSmoke" BorderColor="CornflowerBlue" ForeColor="Black"
                Height="30px" />
            <Columns>
            <asp:TemplateField HeaderText="S.No">
                  <ItemTemplate>
                      <asp:CheckBox ID="chkSelect" runat="server" />
                </ItemTemplate>
                 </asp:TemplateField>
                 <asp:TemplateField HeaderText="S.No">
                  <ItemTemplate>
                    <%# ((GridViewRow)Container).RowIndex + 1%>
                </ItemTemplate>
                </asp:TemplateField>
                <asp:BoundField DataField="Relationship" HeaderText="Relationship" />
                <asp:BoundField DataField="Disease" HeaderText="Disease" />
                <asp:BoundField DataField="Dates" HeaderText="Dates" />
                <asp:TemplateField>
                <ItemTemplate>
                    <asp:Button ID="btnDisplay" runat="server"  /></ItemTemplate>
                </asp:TemplateField>
              </Columns>
            <FooterStyle BackColor="Silver" Height="25px" />
            <PagerStyle BackColor="DarkGray" />
            <HeaderStyle BackColor="#000084" Font-Bold="True" ForeColor="White" />
        </asp:GridView></td></tr>

protected void cmdDiseaseAdd_Click(object sender, EventArgs e)
       {
           List<FmlDiseaseHist> fmlDiseaseList = new List<FmlDiseaseHist>();
           FmlDiseaseHist objFmlDiseaseHist = new FmlDiseaseHist();
           if (chkAddMandatory() == true)
           {
               if (Session["FmlHist"] != null)
               {
                   fmlDiseaseList = (List<FmlDiseaseHist>)(Session["FmlHist"]);
               }

               if (string.IsNullOrEmpty(txtRelation.Text) != true)
               {
                   objFmlDiseaseHist.Relationship = Convert.ToString(txtRelation.Text);
               }
               if (string.IsNullOrEmpty(txtFmlDate.Text) != true)
               {
                   objFmlDiseaseHist.Dates = txtFmlDate.Text;
               }
               if (string.IsNullOrEmpty(txtDisease.Text) != true)
               {
                   objFmlDiseaseHist.Disease = txtDisease.Text;
               }
               txtRelation.Text = "";
               txtFmlDate.Text = dates.Date_Convert(dates.CurDateyyyymmdd());
               txtDisease.Text = "";
               fmlDiseaseList.Add(objFmlDiseaseHist);
               Session["FmlHist"] = fmlDiseaseList;
               grdFmlHist.DataSource = fmlDiseaseList;
               grdFmlHist.DataBind();
           }
       }