CODEWITHSUNDEEP
c#f#websharperjsonconvert
stackh34p
stackh34p

Reputation: 8999

Unable to properly proxy a C# type to client code in an F# WebSharper application

I am experiencing issues when consuming a certain C# type in an F# web application. The following C# type is present in a library I refer to in my F# app:

public static class OuterType
{
    public class Model
    {
        private readonly string id;
        private readonly bool selected;
        private string name;

        internal Model() : this(string.Empty) { }
        public Model(string id) : this(id, false) { }
        public Model(string id, bool selected)
        {
            this.id = name = id;
            this.selected = selected;
        }

        [Localizable(false)]
        public string ID => id;
        public bool Selected => selected;
        [Localizable(true)]
        public string Name
        {
            get => name;
            set => name = value;
        }
    }
}

I have written a proxy for it (as part of my F# web app):

[<Proxy(typeof<OuterType.Model>)>]
type ProxyModel =
    {
        ID : string
        Selected : bool
        Name : string
    }

My project compiles fine, but I am receiving a runtime serialization error:

System.Exception: Error during RPC JSON conversion ---> System.Exception: Failed to look up translated field name for id in type OuterType+Model with fields: Name, Selected, Id

This lead me to believe the converter is looking to match the type by field names. So I changed my proxy as follows:

[<Proxy(typeof<OuterType.Model>)>]
type ProxyModel =
    {
        id : string
        selected : bool
        name : string
    }

The above leads to a compilation error:

WebSharper error FS9001: Could not find field of F# record type: OuterType.Model.Selected WebSharper error FS9001: Could not find field of F# record type: OuterType.Model.Name

and I am stuck. Is there anything I am missing?

Update:

The application is targeting netcoreapp2.1. It uses the following WebSharper dependencies (excerpt from my paket.lock):

WebSharper (4.5.9.330)
WebSharper.AspNetCore (4.5.3.104)
WebSharper.FSharp (4.5.9.330)
WebSharper.Html (4.5.1.153)
WebSharper.Reactive (4.5.1.139)
WebSharper.UI (4.5.8.161)

Upvotes: 1

Views: 101

Answers (1)

Jand
Jand

Reputation: 391

WebSharper remoting uses reflection to create/read objects, so if they are classes, they must follow rules in https://developers.websharper.com/docs/v4.x/cs/remoting#heading-6.

In this case, the only change you need is to make the parameterless constructor public.

Once you have that, you can use the C# type for RPC, but still for client-side use, you need a either [JavaScript] on the type (with WebSharper and WebSharper.CSharp packages added for the C# project), or a proxy that matches it well, including constructors which you won't be able to reproduce with an F# record, you might need a class.

Upvotes: 0

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