How to validate BoundField column in Edit Mode of GridView in ASP.Net

I have managed to do it.

HTML

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" OnRowCreated = "OnRowCreated" OnRowEditing="OnRowEditing">
<Columns>
    <asp:BoundField DataField="Name" HeaderText="Name" ItemStyle-Width="150" />
    <asp:BoundField DataField="Country" HeaderText="Country" ItemStyle-Width="150" />
    <asp:TemplateField>
        <ItemTemplate>
            <asp:LinkButton Text="Edit" runat="server" CommandName="Edit" />
        </ItemTemplate>
        <EditItemTemplate>
            <asp:LinkButton Text="Update" runat="server" OnClick="OnUpdate" />
            <asp:LinkButton Text="Cancel" runat="server" OnClick="OnCancel" />
        </EditItemTemplate>
    </asp:TemplateField>
</Columns>
</asp:GridView>

Namespaces

using System.Data;
using System.Drawing;

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[3] { new DataColumn("Id"), new DataColumn("Name"), new DataColumn("Country") });
        dt.Rows.Add(1, "John Hammond", "");
        dt.Rows.Add(2, "Mudassar Khan", "India");
        dt.Rows.Add(3, "Suzanne Mathews", "France");
        dt.Rows.Add(4, "Robert Schidner", "Russia");
        ViewState["dt"] = dt;
        this.BindGrid();
    }
}

protected void BindGrid()
{
    GridView1.DataSource = ViewState["dt"] as DataTable;
    GridView1.DataBind();
}

protected void OnRowCreated(object sender, GridViewRowEventArgs e)
{
    if (GridView1.EditIndex != -1 && e.Row.RowType == DataControlRowType.DataRow)
    {
        int index = 0;
        foreach (TableCell cell in e.Row.Cells)
        {
            if(cell.Controls.Count > 0)
            {
                if (cell.Controls[0] is TextBox)
                {
                    TextBox textBox = cell.Controls[0] as TextBox;
                    textBox.ID = "txt" + GridView1.HeaderRow.Cells[index].Text.Replace(" ", "");
                    RequiredFieldValidator vaidator = new RequiredFieldValidator
                    {
                        ControlToValidate = textBox.ID,
                        ForeColor = Color.Red,
                        ErrorMessage = "Required",
                        ValidationGroup = "Update"
                    };
                    cell.Controls.Add(vaidator);
                }
                else
                {
                    LinkButton lnkUpdate = cell.Controls.OfType<LinkButton>().Where(lnk => lnk.Text == "Update").FirstOrDefault();
                    if (lnkUpdate != null)
                    {
                        lnkUpdate.ValidationGroup = "Update";
                    }
                }
            }
            index++;
        }
    }
}

protected void OnRowEditing(object sender, GridViewEditEventArgs e)
{
    GridView1.EditIndex = e.NewEditIndex;
    this.BindGrid();
}

protected void OnUpdate(object sender, EventArgs e)
{
    GridViewRow row = (sender as LinkButton).NamingContainer as GridViewRow;
    string name = (row.Cells[0].Controls[0] as TextBox).Text;
    string country = (row.Cells[1].Controls[0] as TextBox).Text;
    DataTable dt = ViewState["dt"] as DataTable;
    dt.Rows[row.RowIndex]["Name"] = name;
    dt.Rows[row.RowIndex]["Country"] = country;
    ViewState["dt"] = dt;
    GridView1.EditIndex = -1;
    this.BindGrid();
}

protected void OnCancel(object sender, EventArgs e)
{
    GridView1.EditIndex = -1;
    this.BindGrid();
}

Screenshot