F＃解析CSV文件-查找错误的行

Question

I wrote this script from some resources I found. It's working but I some files I have problem. I am new in F# so how can I change line with FileHelpersException to get exact line where is the problem? Thanks

// Learn more about F# at http://fsharp.net
// See the 'F# Tutorial' project for more help.
open FileHelpers  
open System

[<DelimitedRecord(",")>]
type CsvRecord =
    class
        val field1 : string
        val field2 : string
        val field3 : int
        new () = {
        field1 = ""
        field2 = ""
        field3 = 0
        }
    end

[<EntryPoint>]
let main argv = 
    use file = System.IO.File.CreateText("result.txt")
    let engine = new FileHelperEngine<CsvRecord>()
    engine.Encoding <- new Text.UTF8Encoding()
    let res = 
       try
          engine.ReadFile("test.csv")
       with
          | :? FileHelpersException -> Array.empty<CsvRecord>
    for record in res do
         fprintfn file "%s" record.field1
    printf "DONE!"
    let s = Console.ReadLine()
    0 // return an integer exit code

Answer 1

I suggest that you use CsvTypeProvider instead. When there's a mismatch the error message states the line which has the error

open FSharp.Data

[<EntryPoint>]
let main argv = 
    use file = System.IO.File.CreateText("result.txt")
    let csv = new CsvProvider<"test.csv">()
    for record in csv.Data do
        fprintfn file "%s" record.field1

If you want to ignore the lines with errors, just pass IgnoreErrors=true as an extra parameter to CsvProvider

Answer 2

This question is about the FileHelpers library you are using, not F#, so looking at the docs for that might help. In this case you can check for ConvertException instead of FileHelpersException , which contains members that give you more details about the member.

try
    engine.ReadFile("test.csv")
with
    | :? ConvertException as ex ->
        printfn "ERROR: Line %d Col %d" ex.LineNumber ex.ColumnNumber
        Array.empty<CsvRecord>

I agree with Gustavo though, you might find it easier to use the CsvTypeProvider.