Please refer below code.
HTML
<div>
<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false" CssClass="Grid"
DataKeyNames="CustomerID" OnRowDataBound="OnRowDataBound">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<img alt="" style="cursor: pointer" src="images/plus.png" />
<asp:Panel ID="pnlOrders" runat="server" Style="display: none">
<asp:GridView ID="gvOrders" runat="server" AutoGenerateColumns="false" CssClass="ChildGrid"
OnRowEditing="OnOrderRowEditing">
<Columns>
<asp:BoundField ItemStyle-Width="150px" DataField="OrderId" HeaderText="Order Id" />
<asp:BoundField ItemStyle-Width="150px" DataField="OrderDate" HeaderText="Date" />
<asp:CommandField ShowEditButton="True" ButtonType="Button" />
</Columns>
</asp:GridView>
</asp:Panel>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField ItemStyle-Width="150px" DataField="ContactName" HeaderText="Contact Name" />
<asp:BoundField ItemStyle-Width="150px" DataField="City" HeaderText="City" />
</Columns>
</asp:GridView>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
$("[src*=plus]").live("click", function () {
$(this).closest("tr").after("<tr><td></td><td colspan = '999'>" + $(this).next().html() + "</td></tr>")
$(this).attr("src", "images/minus.png");
});
$("[src*=minus]").live("click", function () {
$(this).attr("src", "images/plus.png");
$(this).closest("tr").next().remove();
});
</script>
</div>
C#
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
gvCustomers.DataSource = GetData("select top 10 * from Customers");
gvCustomers.DataBind();
}
}
private static DataTable GetData(string query)
{
string strConnString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
using (SqlConnection con = new SqlConnection(strConnString))
{
using (SqlCommand cmd = new SqlCommand())
{
cmd.CommandText = query;
using (SqlDataAdapter sda = new SqlDataAdapter())
{
cmd.Connection = con;
sda.SelectCommand = cmd;
using (DataSet ds = new DataSet())
{
DataTable dt = new DataTable();
sda.Fill(dt);
return dt;
}
}
}
}
}
protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
string customerId = gvCustomers.DataKeys[e.Row.RowIndex].Value.ToString();
GridView gvOrders = e.Row.FindControl("gvOrders") as GridView;
gvOrders.DataSource = GetData(string.Format("select top 3 * from Orders where CustomerId='{0}'", customerId));
gvOrders.DataBind();
}
}
protected void OnOrderRowEditing(object sender, GridViewEditEventArgs e)
{
GridView gvOrder = (sender as GridView);
GridViewRow gvCustomerRow = gvOrder.NamingContainer as GridViewRow;
string customerId = gvCustomers.DataKeys[gvCustomerRow.RowIndex].Value.ToString();
// Do your stuff..
}