How to execute parallel tasks in Web API.

Question

User-1571110992 posted

Hi All,

I have Web API  which included several functions. Each function making another API cal and creating chart object. How I can execute all inner function at once and wait until all task completed.   

 public Chart GetAllData([FromBody]ChartParam s)
        {
          int a =10
          QueryDataIndicatorData(a);
          QueryGetAccess();
          return Charttemp;
        }

Answer 1

User1724605321 posted

Hi vishabedre,

You can create and start the tasks , in each task you can make a call to API to get the response , await each task and finally return the final result in web api . Code below is for your reference :

        // GET api/values
        public async Task<IEnumerable<string>> GetAsync()
        {
            await CreateMultipleTasksAsync();
            return new string[] { "value1", "value2" };
        }
        private async Task CreateMultipleTasksAsync()
        {
            // Declare an HttpClient object, and increase the buffer size. The  
            // default buffer size is 65,536.  
            HttpClient client =
                new HttpClient() { MaxResponseContentBufferSize = 1000000 };

            // Create and start the tasks. As each task finishes, DisplayResults   
            // displays its length.  
            Task<int> download1 =
                ProcessURLAsync("http://msdn.microsoft.com", client);
            Task<int> download2 =
                ProcessURLAsync("http://msdn.microsoft.com/library/hh156528(VS.110).aspx", client);
            Task<int> download3 =
                ProcessURLAsync("http://msdn.microsoft.com/library/67w7t67f.aspx", client);

            // Await each task.  
            int length1 = await download1;
            int length2 = await download2;
            int length3 = await download3;

            int total = length1 + length2 + length3;

            // Display the total count for the downloaded websites.  
          var result =
                string.Format("\r\n\r\nTotal bytes returned:  {0}\r\n", total);
        }

        async Task<int> ProcessURLAsync(string url, HttpClient client)
        {
            var byteArray = await client.GetByteArrayAsync(url);
            DisplayResults(url, byteArray);
            return byteArray.Length;
        }

        private void DisplayResults(string url, byte[] content)
        {
            // Display the length of each website. The string format   
            // is designed to be used with a monospaced font, such as  
            // Lucida Console or Global Monospace.  
            var bytes = content.Length;
            // Strip off the "http://".  
            var displayURL = url.Replace("http://", "");
            var result= string.Format("\n{0,-58} {1,8}", displayURL, bytes);
        }

Best Regards,

Nan Yu

Answer 2

User-1571110992 posted

Thank you for Replay. I just want to execute this two function parallel. And want to make sure both execute successfully before returning output form API.  

 QueryDataIndicatorData(a);
 QueryGetAccess();

 

Answer 3

User1881638666 posted

Hi,

Use await Task.WhenAll

https://msdn.microsoft.com/en-us/library/system.threading.tasks.task.whenall(v=vs.110).aspx

Thanks,

Wenushka

Answer 4

User-1571110992 posted

public async Task<Chart> GetAllDataPart2([FromBody]ChartParam s)
        {
            var tasks = new List<Task>();
            tasks.Add(Task.Run(() => QueryDataCDCPopular(Convert.ToDateTime(s.start_period.Value), Convert.ToDateTime(s.end_period.Value))));
            tasks.Add(Task.Run(() => QueryTeachingResourcesData(Convert.ToDateTime(s.start_period.Value), Convert.ToDateTime(s.end_period.Value))));
         

            await Task.WhenAll(tasks);
}