What is the simplest way to access data of an F# discriminated union type in C#?

Question

I\'m trying to understand how well C# and F# can play together. I\'ve taken some code from the F# for Fun & Profit blog which performs basic validation returning a discr

Answer 1

I had this same issue with the Result type. I created a new type of ResultInterop<'TSuccess, 'TFailure> and a helper method to hydrate the type

type ResultInterop<'TSuccess, 'TFailure> = {
    IsSuccess : bool
    Success : 'TSuccess
    Failure : 'TFailure
}

let toResultInterop result =
    match result with
    | Success s -> { IsSuccess=true; Success=s; Failure=Unchecked.defaultof<_> }
    | Failure f -> { IsSuccess=false; Success=Unchecked.defaultof<_>; Failure=f }

Now I have the choice of piping through toResultInterop at the F# boundary or doing so within the C# code.

At the F# boundary

module MyFSharpModule =
    let validate request = 
        if request.isValid then
            Success "Woot"
        else
            Failure "request not valid"
        
    let handleUpdateRequest request = 
        request
        |> validate
        |> toResultInterop

---

public string Get(Request request)
{
    var result = MyFSharpModule.handleUpdateRequest(request);
    if (result.IsSuccess)
        return result.Success;
    else
        throw new Exception(result.Failure);
}

After the interop in Csharp

module MyFSharpModule =
    let validate request = 
        if request.isValid then
            Success "Woot"
        else
            Failure "request not valid"
        
    let handleUpdateRequest request = request |> validate

---

public string Get(Request request)
{
    var response = MyFSharpModule.handleUpdateRequest(request);
    var result = Interop.toResultInterop(response);
    if (result.IsSuccess)
        return result.Success;
    else
        throw new Exception(result.Failure);
}