How to make Multiple requests in parallel to a webservice in C#

Question

I need to call 3 WCF services as below,

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);

This takes a lot of time to get results and display on the page. Can anyone help me how I could execute them in parallel?

• user1247139: Put this into another class and multithread it?

Answer 1

You can use the task parallelism library:

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;

Or alternatively, since your requests are all very similar, differing only by the url and upload string, you can use LINQ AsParallel array processing:

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];

• Krishh: Thank you very much for your answer. This indeed would speed up the process.
• mellamokb: I did not test any of the code above. Let me know if it generates compile-time or runtime errors. You may also want to familiarize yourself with AggregateException for dealing with errors when one or more of the requests cannot be completed.

Answer 2

You can use the begin/end pattern:

This example shows you how to call two ws in parallell. You can extend the idea to N services.

Answer 3

Try creating a Task that executes each of your calls (MSDN)

You could try doing the following

First create a Task<String> for each of your calls

var client = new WebClient();
client.Headers[HttpRequestHeader.ContentType] = "application/json";
Task<String> task1 = Task.Factory.StartNew(() => {
 client.UploadString("http://localhost:45868/Product/GetAvailableProductsByContact",
 jsonser1);
});

Rinse and repeat for the other 2

Afterwards you can join on the execution of the 3 Task<String> by calling task1.Value, task2.Value and task3.Value which will return a String

• foliveira: @mellamokb beat me to it! His/her 2nd answer is great.
• mellamokb: Note that you want to be careful about sharing the same instance of the client across the parallel tasks. WebClient instances are not declared thread safe, which is why I explicitly go to the effort in my examples to create separate instances of WebClient objects for each service call.