如何在C＃中与Web服务并行发出多个请求

Question

我需要按以下方式致电3个WCF服务，

var client = new WebClient();
    client.Headers[HttpRequestHeader.ContentType] = "application/json";
    var resultJson1 = client.UploadString("http://localhost:45868/Product/GetAvailableProductsByContact",
                                         jsonser1);
var resultJson2= client.UploadString("http://localhost:45868/Product/GetMemberProductsByContact",
                                         jsonser2);

var resultJson3= client.UploadString("http://localhost:45868/Product/GetCoachProductsByContact",
                                         jsonser3);

这需要大量时间才能获得结果并显示在页面上。 谁能帮助我如何并行执行它们？

Answer 1

您可以使用任务并行性库 ：

Task<string>[] taskArray = new Task<string>[]
    {
        Task.Factory.StartNew(() => {
            var client = new WebClient();
            client.Headers[HttpRequestHeader.ContentType] = "application/json";
            var json = client.UploadString("http://localhost:45868/Product/GetAvailableProductsByContact",
                                     jsonser1);
            return json;
        }),
        Task.Factory.StartNew(() => {
            var client = new WebClient();
            client.Headers[HttpRequestHeader.ContentType] = "application/json";
            var json = client.UploadString("http://localhost:45868/Product/GetMemberProductsByContact",
                                     jsonser2);
            return json;
        }),
        Task.Factory.StartNew(() => {
            var client = new WebClient();
            client.Headers[HttpRequestHeader.ContentType] = "application/json";
            var json = client.UploadString("http://localhost:45868/Product/GetCoachProductsByContact",
                                     jsonser3);
            return json;
        }),
    };

// the request for .Result is blocking and waits until each task
// is completed before continuing; however, they should also all
// run in parallel instead of sequentially.
var resultJson1 = taskArray[0].Result;
var resultJson2 = taskArray[1].Result;
var resultJson3 = taskArray[2].Result;

或者，由于您的请求非常相似，仅URL和上载字符串不同，因此可以使用LINQ AsParallel数组处理：

var requests = new [] {
    new { Url = "http://localhost:45868/Product/GetAvailableProductsByContact", Input = jsonser1 },
    new { Url = "http://localhost:45868/Product/GetMemberProductsByContact", Input = jsonser2 },
    new { Url = "http://localhost:45868/Product/GetCoachProductsByContact", Input = jsonser3 },
};
var result = requests.AsParallel().Select(req => {
    var client = new WebClient();
    client.Headers[HttpRequestHeader.ContentType] = "application/json";
    var json = client.UploadString(req.Url, req.Input);
    return json;
}).ToArray();

// when above code has finished running, all tasks are completed
var resultJson1 = result[0];
var resultJson2 = result[1];
var resultJson3 = result[2];

Answer 2

您可以使用开始/结束模式：

本示例说明如何并行调用两个ws。 您可以将其扩展到N个服务。

Answer 3

尝试创建一个执行您的每个调用的Task （ MSDN ）

您可以尝试执行以下操作

首先为每个调用创建一个Task<String>

var client = new WebClient();
client.Headers[HttpRequestHeader.ContentType] = "application/json";

Task<String> task1 = Task.Factory.StartNew(() => {
    client.UploadString("http://localhost:45868/Product/GetAvailableProductsByContact",
                                         jsonser1);
});

冲洗并重复其他2次

之后，您可以通过调用task1.Value ， task2.Value和task3.Value并返回一个String来加入3 Task<String>的执行。