Server code to save uploaded files

Question

This code basically saves an uploaded file to the server. I am wondering if there is anything that I can do to tighten this code up. I am very new to F# so I'm still having trouble breaking away from the C# way of doing things.

/// Create file paths
/// Returns a tuple (server path * link path * file number)
let createPath (file : HttpPostedFileBase) =
 // server directory path
 let serverDirPath = 
 HttpContext.Current.Server.MapPath(@"~/Uploads")
 // get the file name
 let origFileName = file.FileName
 // get the extension
 let extension = Path.GetExtension(origFileName)
 // get the file size in bytes
 let fileSize = file.ContentLength
 // directory check
 let pathExists() = Directory.Exists(serverDirPath)
 // create directory
 let createDir() = 
 if not (pathExists()) then
 Directory.CreateDirectory(serverDirPath) |> ignore
 createDir()
 // find current file name
 let findCurrentFileName() = 
 // check if row exist
 let rowCount = 
 query{
 for row in db.Uploads do
 select row
 count
 }
 // get file number
 let fileNumber = 
 if rowCount < 1
 then
 1
 else
 query{
 for row in db.Uploads do
 select (row.FileNumber + 1)
 head
 }
 // final path
 let finalServPath = 
 serverDirPath + @"\" + fileNumber.ToString() + extension
 // download link
 let linkPath = 
 finalServPath.Replace(serverDirPath + @"\", @"~/Uploads/") 
 finalServPath, linkPath, fileNumber
 findCurrentFileName()
/// Save file to server and path to db.
let SaveUpload (file: HttpPostedFileBase) (title : string) = 
 // create the path including filename
 let servPath, linkPath, fileNumber = createPath file 
 // save file to server
 file.SaveAs(servPath)
 // create new row for db table
 let newUpload = 
 new dbSchema.ServiceTypes.Uploads(Title = title,
 FilePath = servPath,
 Size = file.ContentLength.ToString(),
 FileNumber = fileNumber,
 LinkPath = linkPath)
 // insert new row
 insertRowIn db.Uploads newUpload
 // save to db
 saveToDb()

• Daniel: It looks fine to me. I'd probably define a type for createPath's return value instead of using a 3-tuple. The only other observation is it's unnecessary to check if a directory exists before calling CreateDirectory. It already does that check for you.
• user1206480: Thanks for the comment, Daniel. Can you provide an example of the type to return.
• Daniel: A record would work: type PathInfo = { ServerPath: string; LinkPath: string; FileNumber: int }

Answer 1

I think that you're using comments unnecessarily. If you set a variable called fileNumber, the comment // get file number doesn't tell the reader anything new and only clutters the code.

---

// directory check
let pathExists() = Directory.Exists(serverDirPath)
// create directory
let createDir() = 
 if not (pathExists()) then
 Directory.CreateDirectory(serverDirPath) |> ignore
createDir()

I don't see any reason to have createDir or pathExists as separate functions, since they're short and not reusable.

And as Daniel mentioned in a comment, the check is not actually necessary. So, I would simplify this code to just:

Directory.CreateDirectory(serverDirPath) |> ignore

---

// check if row exist
let rowCount = 
 query{
 for row in db.Uploads do
 select row
 count
 }
// get file number
let fileNumber = 
 if rowCount < 1
 then
 1
 else
 query{
 for row in db.Uploads do
 select (row.FileNumber + 1)
 head
 }

You can use headOrDefault here, to get rid of the first query:

// get file number
let fileNumber = 
 query {
 for row in db.Uploads do
 select row.FileNumber
 headOrDefault
 } + 1

Also, you're not using any ordering in the query, are you sure the largest FileNumber is always going to be the first one?

---

let finalServPath = 
 serverDirPath + @"\" + fileNumber.ToString() + extension

You can use Path.Combine() to concatenate parts of a path:

let finalServPath = 
 Path.Combine(serverDirPath, fileNumber.ToString() + extension)