F# records

[dharmatech]

Here's an F# script that uses CsvHelper and runs as expected:

#r "nuget: CsvHelper, 30.0.1"

open System.IO
open System.Net.Http
open CsvHelper

type WALCLRecord() =
    member val DATE = "" with get, set
    member val WALCL = "" with get, set

let uri = sprintf  "https://fred.stlouisfed.org/graph/fredgraph.csv?id=%s&cosd=%s" "WALCL" "2023-01-01"
        
let str = (new HttpClient()).GetStringAsync(uri).Result

use string_reader = new StringReader(str)
use csv_reader = new CsvReader(string_reader, System.Globalization.CultureInfo.InvariantCulture)

let records = csv_reader.GetRecords<WALCLRecord>()

let arr = records |> Array.ofSeq

for elt in arr do
    printfn "%10s %15s" elt.DATE elt.WALCL

exit 0

Note that it's using a class with properties to hold the data each row:

type WALCLRecord() =
    member val DATE = "" with get, set
    member val WALCL = "" with get, set

If I use an F# record instead:

type WALCLRecord = {
    DATE : string
    WALCL : float
}

it results in the following error:

CsvHelper.HeaderValidationException: Header with name 'dATE'[0] was not found.                                                                                                                           
Header with name 'wALCL'[0] was not found.                                                                                                                                                               
Headers: 'DATE', 'WALCL'                                                                                                                                                                                 
Headers: 'DATE', 'WALCL'                                                                                                                                                                                 
If you are expecting some headers to be missing and want to ignore this validation, set the configuration HeaderValidated to null. You can also change the functionality to do something else, like logging the issue.                                                                                                                                                                                            
                                                                                                                                                                                                         
IReader state:                                                                                                                                                                                           
   ColumnCount: 0                                                                                                                                                                                        
   CurrentIndex: -1                                                                                                                                                                                      
   HeaderRecord:                                                                                                                                                                                         
["DATE","WALCL"]                                                                                                                                                                                         
IParser state:                                                                                                                                                                                           
   ByteCount: 0                                                                                                                                                                                          
   CharCount: 11                                                                                                                                                                                         
   Row: 1                                                                                                                                                                                                
   RawRow: 1                                                                                                                                                                                             
   Count: 2                                                                                                                                                                                              
   RawRecord:                                                                                                                                                                                            
DATE,WALCL                                                                                                                                                                                               
                                                                                                                                                                                                         
                                                                                                                                                                                                         
   at CsvHelper.Configuration.ConfigurationFunctions.HeaderValidated(HeaderValidatedArgs args)                                                                                                           
   at CsvHelper.CsvReader.ValidateHeader(Type type)                                                                                                                                                      
   at CsvHelper.CsvReader.ValidateHeader[T]()                                                                                                                                                            
   at CsvHelper.CsvReader.GetRecords[T]()+MoveNext()                                                                                                                                                     
   at Microsoft.FSharp.Collections.SeqModule.ToArray[T](IEnumerable`1 source) in D:\a\_work\1\s\src\FSharp.Core\seq.fs:line 1037                                                                         
   at <StartupCode$FSI_0183>.$FSI_0183.main@() in c:\Users\dharm\Dropbox\Documents\net-liquidity.fsx\walcl-csvhelper.fsx:line 98                                                                         
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)                                                                                     
   at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr)                                                                                                          
Stopped due to error                   

Question

Is there a way to use the record type with CsvHelper?

[dharmatech]

I've posted the question here:

https://stackoverflow.com/questions/76361833/csvhelper-with-f-records

If this question is more appropriate there, feel free to remove this one. :-)