This error occurs when you try to save the file in the desired folder using the ASP.net file upload control.
HttpPostedFile myFile = fileUpload.PostedFile;
myFile.SaveAs(Server.MapPath("\\news\\") + myFile.FileName);
The above line will generate the error. As it will try to save the file in the path :
C:\home\sites\xyz\news\C:\Upload\filetoupload.txt
which is invalid format because of c:\ being used twice and hence you getting the
invalid format error.
When working with file names and paths it's recommended to use System.IO.Path-class
So use
myFile.SaveAs(Server.MapPath("\\news\\") + System.IO.Path.GetFileName(myFile.FileName));
Hoping that this will help.
:)
