deleting a row from gridview

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ASP.NET

hi
i am adding data from textboxes to grid view.
here is no problem in adding a row
problem is with deleting
i have to delete rows from grid view if a row is checked in the gridview
i dont want to make any changes in database

here is my sample code

<table><tr>
 <td><asp:Label ID="lblFmlDate" runat="server" Text="Date"></td>
                <td><asp:TextBox ID="txtFmlDate"  runat="server" Enabled ="False">
                    <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">
                    
            </td></tr>
            <tr>
            <td><asp:Label ID="lblDisease" runat="server" Text="Disease"></td>
            <td><asp:TextBox ID="txtDisease" Enabled ="False" runat="server" ></td>
            <td><asp:Button ID="cmdDiseaseAdd" Enabled ="False" runat="server" Text="Add" 
                    width="60px" onclick="cmdDiseaseAdd_Click" /></td>
            <td><asp:Button ID="cmdDiseaseDel" Enabled ="False" runat="server" Text="Delete" 
                    width="60px" onclick="cmdDiseaseDel_Click"/></td>
            </tr><tr>
            <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" AutoGenerateDeleteButton="True" 
                    onrowdeleting="grdFmlHist_RowDeleting" >
            <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 HeaderText="S.No">
                  <itemtemplate>
                    <%# ((GridViewRow)Container).RowIndex + 1%>
                </itemtemplate>
                
                <asp:BoundField DataField="Relationship" HeaderText="Relationship" />
                <asp:BoundField DataField="Disease" HeaderText="Disease" />
                <asp:BoundField DataField="Dates" HeaderText="Dates" />
              </columns>
            <footerstyle backcolor="Silver" height="25px" />
            <pagerstyle backcolor="DarkGray" />
            <HeaderStyle BackColor="#000084" Font-Bold="True" ForeColor="White" />
        
            </rowstyle></td></tr></table>

source code

 protected void cmdDiseaseAdd_Click(object sender, EventArgs e)
        {
            List<fmldiseasehist> fmlDiseaseList = new List<fmldiseasehist>();
            FmlDiseaseHist objFmlDiseaseHist = new FmlDiseaseHist();
            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();
           
         }
 protected void cmdDiseaseDel_Click(object sender, EventArgs e)
        {
            List<fmldiseasehist> fmlDiseaseList = new List<fmldiseasehist>();
            CheckBox chk = new CheckBox();
            if (chkDelMandatory ()== true)
            {
               foreach (GridViewRow gvr in grdFmlHist.Rows)
                        {
                            chk = (CheckBox)(gvr.Cells[0].FindControl("chkSelect"));
                            if (chk.Checked == true)
                            {
                                grdFmlHist.DeleteRow(gvr.RowIndex);
                            }
                        }
                           
            }
           
       }
protected void grdFmlHist_RowDeleting(object sender, GridViewDeleteEventArgs e)
        {
        }