返回通用对象类型

Question

我们在GitHub Gist上的完整代码我只包括我认为需要显示问题的部分。

执行方法：

  public object Execute()
        {
            var request = createWebRequest();
            request.Method = this.Method;
            applyPostData(ref request);

            request.ContentType = "application/json";
            request.UserAgent = "generic-http-dotnet-client/3.5/v1 (gzip)";

            var response = (HttpWebResponse)request.GetResponse();

            var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

            try
            {
                return JsonConvert.DeserializeObject(responseString);
            }
            catch (Exception)
            {
                return new HttpResponse { message = responseString };
            }
        }

好的，这很有效。但是，我希望能够在调用该方法后将其转换为适当的对象类型。

var response = (MetaDataResponse)request.Execute();

我知道应该有某种方式可能使用泛型（疯狂猜测）让我对响应进行 json DeserializeObject 并返回它？

我最终将执行方法的返回类型更改为字符串，并执行此操作。

public class MetaDataRequest : HttpRequestBase
    {
        public MetaDataResponse MetaDataItems { get; private set; }

        public MetaDataRequest() : base(new Uri("https://www.googleapis.com/analytics/v3/metadata/ga/columns"), "GET")
        {
            this.addParameter("key", "xxxx");
            var response = this.Execute();

            try
            {
                MetaDataItems =  JsonConvert.DeserializeObject<MetaDataResponse>(response);
            }
            catch (Exception)
            {
                var resultsx = new HttpResponse { message = response };
            }
        }
    }

这很有效，但对我来说很乱。请注意，该项目是 .Net framework 3.5，我无法更改。随意添加您能想到的任何其他标签。

Answer 1

首先，要点不是处理它的 IDisposables，这很草率。我会推荐这样的东西：

public T Execute<T>()
    {
        var request = createWebRequest();
        request.Method = this.Method;
        applyPostData(ref request);

        request.ContentType = "application/json";
        request.UserAgent = "generic-http-dotnet-client/3.5/v1 (gzip)";

        using(var response = (HttpWebResponse)request.GetResponse())
        using(var stream = response.GetResponseStream())
        using(var reader = new StreamReader(stream))
        {
            try
            {
                var responseString = reader.ReadToEnd();
                return JsonConvert.DeserializeObject<T>(responseString);
            }
            catch (Exception ex)
            {
                //log something with ex
                return default(T);
            }
        }
    }

Answer 2

对 MetaDataRequest 类使用泛型

class MetadataRequest<T>:HttpRequestBase
{
    public T Execute()
    {
        var request = createWebRequest();
        request.Method = this.Method;
        applyPostData(ref request);

        request.ContentType = "application/json";
        request.UserAgent = "generic-http-dotnet-client/3.5/v1 (gzip)";

        var response = (HttpWebResponse)request.GetResponse();

        var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

        return JsonConvert.DeserializeObject<T>(responseString);
    }
}

然后，要获取对象，您可以像这样调用方法：

MetadataResponse responseObject = (new MetadataRequest<MetadataResponse>()).Execute();

在这种情况下，您可以捕获 .Execute() 抛出的异常，因为它只能返回 null 或 T 类型的实例。

编辑：您也可以按照Jeremy Holovacs' answer 使用泛型方法。