Asynchronous mainly used to enhance program performance, will increase the cost of the system (a new thread to perform asynchronous tasks).
It can be applied to time-consuming tasks, such as: when accessing the database (the application database and not on the same server), calls between service (service will be distributed on different servers).
About the asynchronous call does not return value
First define two methods
New tasks and enables asynchronous
transfer
Output
It is seen through this example two methods are performed simultaneously
Here are no return values of reference example
The definition of a method named GetNum
By calling Task
Output
Likewise, also the two methods simultaneously