How to select & delete record from gridview control

First Create a website in asp.net using c# & design the page

<asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSource1" Style="font-family: Arial;|
font-size: 10pt" AutoGenerateColumns="false" DataKeyNames="sr_no" Width="222px">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:CheckBox ID="chkdelete" runat="server" />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="sr_no" HeaderText="Sr.No" />
<asp:BoundField DataField="disease_name" HeaderText="Disease" />
</Columns>
</asp:GridView>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Delete" />
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:shivkamal_webConnectionString %>"
SelectCommand="SELECT * FROM [disease_wise_tbl]" DeleteCommand="delete from disease_wise_tbl where sr_no=@sr_no">
<DeleteParameters>
<asp:Parameter Name="sr_no" Type="Int32" />
</DeleteParameters>
</asp:SqlDataSource>
after succefully design the page write the code on button click event foreach (GridViewRow
gvrow in GridView1.Rows) { CheckBox chkdelete = (CheckBox)gvrow.FindControl("chkdelete");
if (chkdelete.Checked) { //Getting UserId of particular row using datakey value
int usrid = Convert.ToInt32(GridView1.DataKeys[gvrow.RowIndex].Value); SqlDataSource1.DeleteParameters["sr_no"].DefaultValue
= usrid.ToString(); SqlDataSource1.Delete();
}
}