Save,Update and Delete in Xml file in Asp.Net

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" CellPadding="4"
ForeColor="#333333" GridLines="None" ShowFooter="True"
 OnRowCancelingEdit="GridView1_RowCancelingEdit"
 OnRowCommand="GridView1_RowCommand" 
OnRowDeleting="GridView1_RowDeleting" 
OnRowEditing="GridView1_RowEditing" 
OnRowUpdating="GridView1_RowUpdating">
<FooterStyle BackColor="#990000" Font-Bold="True" ForeColor="White" />
<Columns>
<asp:TemplateField HeaderText="Eno">
<EditItemTemplate>
<asp:Label ID="Label2" runat="server" Text='<%# Eval("eno") %>'></asp:Label>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Eval("eno") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Name">
<EditItemTemplate>
<asp:TextBox ID="TextBox2" runat="server" Text='<%# Eval("ename") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="Label3" runat="server" Text='<%# Eval("ename") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Address">
<EditItemTemplate>
<asp:TextBox ID="TextBox4" runat="server" Text='<%# Eval("eadd") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="TextBox5" runat="server"></asp:TextBox>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="Label4" runat="server" Text='<%# Eval("eadd") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Salary">
<EditItemTemplate>
<asp:TextBox ID="TextBox6" runat="server" Text='<%# Eval("esal") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="TextBox7" runat="server"></asp:TextBox>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="Label5" runat="server" Text='<%# Eval("esal") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Edit">
<EditItemTemplate>
<asp:LinkButton ID="LinkButton3" runat="server" CommandName="update">Update</asp:LinkButton>
<asp:LinkButton ID="LinkButton4" runat="server" CommandName="cancel">Cancel</asp:LinkButton>
</EditItemTemplate>
<FooterTemplate>
<asp:LinkButton ID="LinkButton5" runat="server" CommandName="save">Save</asp:LinkButton>
</FooterTemplate>
<ItemTemplate>
<asp:LinkButton ID="LinkButton1" runat="server" CommandName="edit">Edit</asp:LinkButton>
<asp:LinkButton ID="LinkButton2" runat="server" CommandName="delete">Delete</asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
</Columns>
<RowStyle BackColor="#FFFBD6" ForeColor="#333333" />
<EmptyDataTemplate>
No Data Available
</EmptyDataTemplate>
<SelectedRowStyle BackColor="#FFCC66" Font-Bold="True" 
ForeColor="Navy" />
<PagerStyle BackColor="#FFCC66" ForeColor="#333333" HorizontalAlign="Center" />
<HeaderStyle BackColor="#990000" Font-Bold="True" ForeColor="White" />
<AlternatingRowStyle BackColor="White" />
</asp:GridView>

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;

String st = Server.MapPath("emp.xml");
if (Page.IsPostBack == false)
{
if(File.Exists(st)==false)
createxml();
getxml();
}

//Method Creating Xml File if does'nt Exists
private void createxml()
{
DataTable tb = new DataTable("emptable");
tb.Columns.Add("eno", Type.GetType("System.Int32"));
tb.Columns.Add("ename", Type.GetType("System.String"));
tb.Columns.Add("eadd", Type.GetType("System.String"));
tb.Columns.Add("esal", Type.GetType("System.Int32"));
DataRow r = tb.NewRow();
r[0] = 1;
r[1]="Rahul Choudhary";
r[2] ="Chandigarh";
r[3] =12000;
tb.Rows.Add(r);
String st = Server.MapPath("emp.xml");
tb.WriteXml(st);
}

//Method to bind Grid view
private void getxml()
{
String st = Server.MapPath("emp.xml");
DataSet ds = new DataSet();
ds.ReadXml(st);
GridView1.DataSource = ds;
GridView1.DataBind();
} 

//Grid View Event to Save Data into Xml File
protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "save")
{
String st = Server.MapPath("emp.xml");
DataSet ds = new DataSet();
ds.ReadXml(st);
DataRow r = ds.Tables[0].NewRow();
r[0] = Convert.ToInt32(((TextBox)(GridView1.FooterRow.FindControl("TextBox1"))).Text);
r[1] = ((TextBox)(GridView1.FooterRow.FindControl("TextBox3"))).Text;
r[2] = ((TextBox)(GridView1.FooterRow.FindControl("TextBox5"))).Text;
r[3] = Convert.ToInt32(((TextBox)(GridView1.FooterRow.FindControl("TextBox7"))).Text);
ds.Tables[0].Rows.Add(r);
ds.WriteXml(st);
getxml();
}
}

//Grid View Row Deleting Event to Delete From Xml File
protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
String st = Server.MapPath("emp.xml");
DataSet ds = new DataSet();
ds.ReadXml(st);
ds.Tables[0].Rows.RemoveAt(e.RowIndex);
ds.WriteXml(st);
getxml();
}
protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
{
GridView1.EditIndex = e.NewEditIndex;
getxml();
}
protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
{
GridView1.EditIndex = -1;
getxml();
}

//Grid View row Updating Event to update xml file
protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
String st = Server.MapPath("emp.xml");
DataSet ds = new DataSet();
ds.ReadXml(st);
ds.Tables[0].Rows[e.RowIndex][1] = ((TextBox)(GridView1.Rows[e.RowIndex].FindControl("TextBox2"))).Text;
ds.Tables[0].Rows[e.RowIndex][2] = ((TextBox)(GridView1.Rows[e.RowIndex].FindControl("TextBox4"))).Text;
ds.Tables[0].Rows[e.RowIndex][3] = Convert.ToInt32(((TextBox)(GridView1.Rows[e.RowIndex].FindControl("TextBox6"))).Text);
GridView1.EditIndex = -1;
ds.WriteXml(st);
getxml();
}