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WPF generic value converter for Discriminated Unions

A generic value converter for discriminated unions, it allows to use a single converter for any discriminated union along with facilitating the creation of new ones with a default option value for when an incompatible union case is provided. Large part of this snippet uses http://fssnip.net/62 as a base, all credit on the ConverterBase goes to him, one of the authors also has a new version of it http://fssnip.net/7Q

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//For the following snippet to work it requires a ConverterBase which is provided in this snippet http://fssnip.net/62 from a different author.

type DiscriminatedUnionTypeConverterGeneric<'a>(defaultOnError : 'a option) =
    inherit ConverterBase()
    let convertFunc = fun (v:obj) _ _ _ -> box (string v)
    let convertBackFunc = fun (v:obj) _ _ _ ->
        if ((unbox v).GetType().Name = "String") && defaultOnError.IsSome
        then box defaultOnError.Value
        else v
    override this.Convert = convertFunc 
    override this.ConvertBack = convertBackFunc


type DiscriminatedUnionTypeConverter() =
    inherit DiscriminatedUnionTypeConverterGeneric<ConverterBase>(None)

//Usage:
// Either use the DiscriminatedUnionTypeConverter, or create your own with a default option for when a wrong union case is provided to the converter like so:

//type ExampleDiscriminatedUnionTypeConverter() =
//    inherit DiscriminatedUnionTypeConverterGeneric<ExampleDiscriminatedUnion>(Some ExampleDiscriminatedUnion.CarCase)

// In this case if a wrong union case is provided the convertBackFunc will provide the defaultOnError value.

Multiple items
type DiscriminatedUnionTypeConverterGeneric<'a> =
  inherit obj
  new : defaultOnError:'a option -> DiscriminatedUnionTypeConverterGeneric<'a>
  override Convert : 'b
  override ConvertBack : 'b

Full name: Script.DiscriminatedUnionTypeConverterGeneric<_>

--------------------
new : defaultOnError:'a option -> DiscriminatedUnionTypeConverterGeneric<'a>

val defaultOnError : 'a option

type 'T option = Option<'T>

Full name: Microsoft.FSharp.Core.option<_>

type obj = System.Object

Full name: Microsoft.FSharp.Core.obj

val box : value:'T -> obj

Full name: Microsoft.FSharp.Core.Operators.box

Multiple items
val string : value:'T -> string

Full name: Microsoft.FSharp.Core.Operators.string

--------------------
type string = System.String

Full name: Microsoft.FSharp.Core.string

val unbox : value:obj -> 'T

Full name: Microsoft.FSharp.Core.Operators.unbox

override DiscriminatedUnionTypeConverterGeneric.Convert : 'b

Full name: Script.DiscriminatedUnionTypeConverterGeneric`1.Convert

override DiscriminatedUnionTypeConverterGeneric.ConvertBack : 'b

Full name: Script.DiscriminatedUnionTypeConverterGeneric`1.ConvertBack

Multiple items
type DiscriminatedUnionTypeConverter =
inherit obj
new : unit -> DiscriminatedUnionTypeConverter

Full name: Script.DiscriminatedUnionTypeConverter

--------------------
new : unit -> DiscriminatedUnionTypeConverter

union case Option.None: Option<'T>

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More information

Link:	http://fssnip.net/7VO
Posted:	6 years ago
Author:	Micael Morais
Tags:	discriminated union , silverlight , wpf