如何使用graphql.net核心2中间件包装asp.net端点响应？

Question

我使用asp.net web api2开发了REST。我正在使用REST核心2将REST迁移到GraphQL.net端点。在现有的REST代码中，我有一个委托处理程序，用于用附加数据扩展REST调用的结果，在本例中是将本地化数据添加到response.Since委托处理程序，在asp.net核心2中不再支持。我试图将现有的委托处理程序迁移到中间件组件。

为便于参考，我遵循了以下内容：使用OWIN中间件扩展WebApi响应和https://www.devtrends.co.uk/blog/wrapping-asp.net-web-api-responses-for-consistency-and-to-provide-additional-information

在这里，我有几个问题：

1. 如何在中间件的情况下映射下面的代码？变量响应=等待base.SendAsync(请求，cancellationToken)；
2. 我应该把中间件放在Startup.cs配置方法中。
3. 与现有委托处理程序等效的中间件

代码：

public class CommonResponserHandler : DelegatingHandler
{
    ICommonService _commonService = new CommonService();
    protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        string locale = string.Empty;
        if (request.Headers.Contains("Accept-Language"))
        {
            locale = request.Headers.GetValues("Accept-Language").First();
        }

        bool initialAuthorizationStatus = GetInitialAuthorization(request);
        var response = await base.SendAsync(request, cancellationToken);
        APIResult commonResponse;
        if (response.TryGetContentValue<APIResult>(out commonResponse))
        {
            //populate common response here;
            UpdateCommonResponse(request, response, commonResponse);
            //UpdateCommonResponse(basicResponse, commonResponse);
            HttpResponseMessage newResponse;
            bool authorizatinCheckResult = AssertAuthorization(initialAuthorizationStatus, request);
            if (authorizatinCheckResult)
            {
                newResponse = request.CreateResponse(response.StatusCode, commonResponse);
            }
            else
            {
                var unAuthorisedResult = new APIResult{Authorized = false, UserMessage = Constants.Unauthorized, Locale = new Locale(_commonService.GetLanguageFromLocale(locale))};
                newResponse = request.CreateResponse(HttpStatusCode.Unauthorized, unAuthorisedResult);
                var jsonSerializerSettings = new JsonSerializerSettings{ContractResolver = new CamelCasePropertyNamesContractResolver()};
                HttpContext.Current.Items["401message"] = JsonConvert.SerializeObject(unAuthorisedResult, Formatting.Indented, jsonSerializerSettings);
            }

            //Add headers from old response to new response
            foreach (var header in response.Headers)
            {
                newResponse.Headers.Add(header.Key, header.Value);
            }

            return newResponse;
        }

        return response;
    }
}

有人能帮我解决这个问题吗？

Answer 1

请阅读ASP.NET核心中间件文档以更好地理解中间件的工作原理。

中间件在其构造函数中接受下一个RequestDelegate，并支持调用方法.For示例：

 public class CommonResponserMiddleware
{
    private readonly RequestDelegate _next;

    public CommonResponserMiddleware(RequestDelegate next)
    {
        _next = next;

    }

    public async Task Invoke(HttpContext context)
    {
        //process context.Request

        await _next.Invoke(context);

        //process context.Response

    }
}

public static class CommonResponserExtensions
{
    public static IApplicationBuilder UseCommonResponser(this IApplicationBuilder builder)
    {
        return builder.UseMiddleware<CommonResponserMiddleware>();
    }
}

并在Starup.cs中使用：

public void Configure(IApplicationBuilder app) {
    //...other configuration

    app.UseCommonResponser();

    //...other configuration
}

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