Question

I followed the link of parse CSV using F# and filehelpers. got compiler error for the following code "The record class oneRow need a constructor with no args (public or private)"

[<DelimitedRecord(",")>]
type oneRow=
  class
    [<FieldConverter(ConverterKind.Date, "M/d/yyyy")>]
    val date: DateTime
    val value: bool
  end
let engine = new FileHelperEngine(typeof<oneRow>)
let tmp = engine.ReadFile("test.csv")

EDIT
The solution looks quite verbose than c# version. I need add (), mutable and [<DefaultValue>]

  type oneRow() =
      class
        [<FieldConverter(ConverterKind.Date, "M/d/yyyy")>]
        [<DefaultValue>]
        val mutable date: DateTime
        [<DefaultValue>]
        val mutable value: bool
      end

But similar code works in C# without specify a constructor. Could anyone help me fix the F# code? thanks.

Answer 1

C# will create you a constructor. F# doesn’t (presumably because parameterless constructors imply mutability, and so are not exactly encouraged.)

For example, in your code – how are you going to set those properties, they’re still immutable.