The Task class also provides constructors that initialize the task but that do not schedule it for execution. For performance reasons, the Task.Run or TaskFactory.StartNew method is the preferred mechanism for creating and scheduling computational tasks, but for scenarios where creation and scheduling must be separated, you can use the constructors and then call the Task.Start method to schedule the task for execution at a later time. 

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sample execution time
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Data1:@ViewBag.GetData1
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Data2:@ViewBag.GetData1
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Data3:@ViewBag.GetData1
<br />
Data4:@ViewBag.GetData1
<br />
execution time:@ViewBag.btime
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After Useing tasking execution time
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Data1: @ViewBag.Data1
<br />
Data2: @ViewBag.Data1
<br />
Data3: @ViewBag.Data1
<br />
Data4: @ViewBag.Data1
<br />
execution time:@ViewBag.time 
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 public ActionResult Index(){ 
Stopwatch stopWatch = new Stopwatch();
stopWatch.Start(); 
ViewBag.GetData1=   GetData1();
  ViewBag.GetData2 = GetData2();
 ViewBag.GetData3 = GetData3();
ViewBag.GetData4 = GetData4();
stopWatch.Stop();
ViewBag.btime = stopWatch.ElapsedMilliseconds;
Stopwatch Watch = new Stopwatch(); 
Watch.Start(); 
Task<string> t1 = Task.Factory.StartNew<string>(GetData1);
Task<string> t2 = Task.Factory.StartNew<string>(GetData2);
Task<string> t3 = Task.Factory.StartNew<string>(GetData3);
Task<string> t4 = Task.Factory.StartNew<string>(GetData4);
Task.WaitAll(t1, t2, t3, t4);  
 ViewBag.Data1 = t1.Result;
ViewBag.Data2 = t2.Result;
ViewBag.Data3 = t3.Result;
 ViewBag.Data4 = t4.Result;
 Watch.Stop();
ViewBag.time = Watch.ElapsedMilliseconds;  
return View();  
 }  
public string GetData1()
{
 System.Threading.Thread.Sleep(1000);
 return "Content 1";  
} 
 public string GetData2()
{ 
  System.Threading.Thread.Sleep(1000);
 return "Content 1"; 
} 
 public string GetData3() 
      {            System.Threading.Thread.Sleep(1000);
            return "Content 4";
        } 
public string GetData4()  {
    System.Threading.Thread.Sleep(1000);
     return "Content 1";
 
}