Here is the code to upload image in web server
if (Fileuploader1.FileName != "")
{
if (File.Exists(Server.MapPath("../images/" + "imagename" + ".jpg")))
File.Delete(Server.MapPath("../images/" + "imagename" + ".jpg"));
Fileuploader1.SaveAs(Server.MapPath("../images/" + "imagename" + ".jpg"));
}
Hope you are storing image path in your database; while updating image update image path in database.
Before applying this check server can be modified by user else you cannot upload image.
If any further query feel free to ask.