i have used it once same as u except FileUpload1.FileName.ToString(); this i have used FileUpload1.FileName;
for exmpal
string img = Server.MapPath("/WebSiteName/FolderName_where_To_savePhotos/");
img += FileUpload1.FileName;
FileUpload1.SaveAs(img);
or try
string fileName = Path.GetFileName(FileUpload1.PostedFile.FileName);
FileUpload1.PostedFile.SaveAs(Server.MapPath("~/WebSiteName/FolderName_where_To_savePhotos/") + fileName);
u also have take care of same name of photos....for that also use some logic