Protected Sub GridView1_RowCommand(sender As Object, e As GridViewCommandEventArgs)
	If e.CommandName = "save" Then
		Dim st As String = Server.MapPath("emp.xml")
		Dim ds As New DataSet()
		ds.ReadXml(st)
		Dim r As DataRow = ds.Tables(0).NewRow()
		r(0) = Convert.ToInt32(DirectCast(GridView1.FooterRow.FindControl("TextBox1"), TextBox).Text)
		r(1) = DirectCast(GridView1.FooterRow.FindControl("TextBox3"), TextBox).Text
		r(2) = DirectCast(GridView1.FooterRow.FindControl("TextBox5"), TextBox).Text
		r(3) = Convert.ToInt32(DirectCast(GridView1.FooterRow.FindControl("TextBox7"), TextBox).Text)
		ds.Tables(0).Rows.Add(r)
		ds.WriteXml(st)
		getxml()
	End If
End Sub

this code will show you how to save data from gridview to xml file

Saving data from gridview to xml file

xml, aspnet

VB.NET