将LINQ(跳过和获取)方法与HttpClient.GetAsync方法一起使用以提高性能吗?

问题描述

我已经使用以下代码来检索JSON feed的内容，并且如您所见，我已经使用了分页技术以及Skip和Take这样的方法:

I have used the following code to retrieve the content of a JSON feed and as you see I have used the paging techniques and Skip and Take methods like this:

[HttpGet("[action]")]
public async Task<myPaginatedReturnedData> MyMethod(int page)
{
    int perPage = 10;
    int start = (page - 1) * perPage;

    using (HttpClient client = new HttpClient())
    {
        client.BaseAddress = new Uri("externalAPI");
        MediaTypeWithQualityHeaderValue contentType =
            new MediaTypeWithQualityHeaderValue("application/json");
        client.DefaultRequestHeaders.Accept.Add(contentType);
        HttpResponseMessage response = await client.GetAsync(client.BaseAddress);
        string content = await response.Content.ReadAsStringAsync();
        IEnumerable<myReturnedData> data = 
               JsonConvert.DeserializeObject<IEnumerable<myReturnedData>>(content);
        myPaginatedReturnedData datasent = new myPaginatedReturnedData
        {
            Count = data.Count(),
            myReturnedData = data.Skip(start).Take(perPage).ToList(),
        };
        return datasent;
    }
}

我的分页工作正常，但是我看不到任何性能改进，我知道这是因为每次我请求一个新页面时，它都会一次又一次地调用API，并在检索所有内容之后，使用Skip和Take方法，我正在寻找一种将Skip和Take方法与我的HttpClient一起应用的方法，以便它仅检索每个页面所需的记录.是否有可能?如果可以，怎么办?

My paging works fine, however I can't see any performance improvement and I know this is because every time I request a new page it calls the API again and again and after retrieving all contents, it filters it using Skip and Take methods, I am looking for a way to apply the Skip and Take methods with my HttpClient so that it only retrieves the needed records for every page. Is it possible? If so, how?

推荐答案

为了将Take/Skip应用于数据检索，服务器必须了解它们.您可以使用IQueryable LINQ提供程序(请参见[1]仅了解其复杂程度)来做到这一点，或者更好的方法是，将适当的值传递给client.GetAsync调用，例如

In order to apply the Take/Skip to the data retrieval, the server would have to know about them. You could do that with an IQueryable LINQ provider (see [1] for getting only an idea of how complex that is) or, better, by passing the appropriate values to the client.GetAsync call, something like

HttpResponseMessage response = await client.GetAsync(client.BaseAddress + $"?skip={start}&take={perPage}");

当然，您的服务器端代码必须正确解释那些skip和take参数.这不是自动的.

Of course, your server-side code has to interpret those skip and take parameters correctly; it's not automatic.

您可能还想看一下OData(请参阅[2])，但是我从未在生产中实际使用过它.我只知道它存在.

You might also want to look at OData (see [2]), but I have never actually used it in production; I just know it exists.

[1] https://msdn.microsoft.com/zh-我们/library/bb546158.aspx

[2] https://docs.microsoft.com/zh-cn/aspnet/web-api/overview/odata-support-in- aspnet-web-api/odata-v3/从一个网络客户端调用一个odata-service-

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