Question

我有一个C＃web api用于访问F＃库。我创建了一个我想要返回的类型的DU，并使用模式匹配来选择哪个返回到c＃控制器。

在C＃控制器中，如何访问从函数调用返回到F＃库的类型的数据？

C＃Controller

public HttpResponseMessage Post()
{
    var _result = Authentication.GetAuthBehaviour();
    //Access item1 of my tuple
    var _HTTPStatusCode = (HttpStatusCode)_result.item1;
    //Access item2 of my tuple
    var _body = (HttpStatusCode)_result.item2;
    return base.Request.CreateResponse(_HTTPStatusCode, _body);
}

F＃Types

module Types =
    [<JsonObject(MemberSerialization=MemberSerialization.OptOut)>]
    [<CLIMutable>]
    type ValidResponse = {
         odata: string;
         token: string; 
    }

    [<JsonObject(MemberSerialization=MemberSerialization.OptOut)>]
    [<CLIMutable>]
    type ErrorResponse = {
         code: string;
         message: string;
         url: string; 
    }

    type AuthenticationResponse = 
    | Valid of int * ValidResponse
    | Error of int * ErrorResponse

F＃功能

module Authentication = 
    open Newtonsoft.Json

    let GetAuthBehaviour () =
        let behaviour = GetBehaviour.Value.authentication
        match behaviour.statusCode with
        | 200 ->
            let deserializedAuthenticationResponse = JsonConvert.DeserializeObject<Types.ValidResponse>(behaviour.body)
            Types.Valid (behaviour.statusCode, deserializedAuthenticationResponse)
        | _ ->
            let deserializedAuthenticationResponse = JsonConvert.DeserializeObject<Types.ErrorResponse>(behaviour.body)
            Types.Error (behaviour.statusCode, deserializedAuthenticationResponse)

Answer 1

F＃Discriminated Unions被编译为抽象类，每个案例都是派生的嵌套类。在C＃中，您可以尝试从GetAuthBehaviour：

向下转换结果来访问案例

public HttpResponseMessage Post()
{
    var result = Authentication.GetAuthBehaviour();

    var valid = result as Types.AuthenticationResponse.Valid;
    if (valid != null)
    {
        int statusCode = valid.Item1;
        Types.ValidResponse body = valid.Item2;
        return this.CreateResponse(statusCode, body);
    }

    var error = result as Types.AuthenticationResponse.Error;
    if (error != null)
    {
        int statusCode = error.Item1;
        Types.ErrorResponse body = error.Item2;
        return this.CreateResponse(statusCode, body);
    }

    throw new InvalidOperationException("...");
}

请注意，C＃编译器并不知道您已经处理了所有情况，因此您需要提供一个处理result不是{{Valid的情况的分支。 1}}也不Error。在这里，我只是抛出异常作为示例，但在Web API中，返回500状态代码可能更合适。

尽管如此，为什么甚至会在C＃中编写和维护控制器？你可以write an ASP.NET Web API purely in F#。

在C＃中使用F＃类型

1 个答案: