How to create new folder if file is allread present ?

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MVC5

ASP.NET5

i am uploading image but if some image with same name then image override ...!! so what can i do ??
may i have to create new folder to store this image ? or what other possibly solution ??

if i have to create new folder then how this posible what code i have to write ??

What I have tried:

[HttpPost]
public ActionResult Index(upload upload,HttpPostedFileBase File)
{

if (File == null)
{
ModelState.AddModelError("customeerror", "Please Upload Your file");
}


try
{
// string filename = Guid.NewGuid() + Path.GetExtension(File.FileName);
string filename = Path.GetFileName(File.FileName);
File.SaveAs(Path.Combine(Server.MapPath("~/uploadcv"), filename));
using (NGOEntities1 db = new NGOEntities1())
{
upload.resume = filename;
db.uploads.Add(upload);
db.SaveChanges();
}
ModelState.Clear();
upload = null;
ViewBag.message = "Succcess";


}
catch(Exception Ex)
{
ViewBag.message = "Error";
return View();
}
return RedirectToAction("list");
}