Sum all of the lines in a given file which are integers

SumFile.fs

open System.IO

// sums up all of the lines in a given file
let sumFile (fileName:string) =
    // wrapper for catching int conversion exceptions
    let wrapper (sr:System.IO.StreamReader) =
        try
            int (sr.ReadLine())
        with
        | :? System.FormatException -> 0

    // sequence generator for lines in the file
    let readLines (path:string) = seq {
        use sr = new StreamReader(path)
        while not sr.EndOfStream do
            yield wrapper sr
    }

    // sum them all together
    Seq.sum (readLines fileName)

[<EntryPoint>]
let main_sumFile (argv:array<string>) =
    // 1 value provided; sum the given file; clean exit
    if argv.Length = 1 then
        printfn "%d" (sumFile argv.[0])
        0
    // wrong number of parameters; display help message; dirty exit
    else
        printfn "Syntax: SumFile.exe <file name>"
        1