To delete a file on server you can use code like this
[ C# ]
// We need this namespace
using System.IO;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string FileToDelete;
// Set full path to file
FileToDelete = Server.MapPath("~/Files/SomeFile.txt");
// Delete a file
File.Delete(FileToDelete);
}
}