Example of the usage of asynchronous callback function in C#

static void Main(string[] args)
{
 Func<string,string> showMessage = ShowMessage;
 //The callback function Completed is set, and there is no return value IAsyncResult result = ("Test asynchronous delegation",new AsyncCallback(Completed),null);
 //Whether the half-segment asynchronous ends while(!)
 {
  ("The main thread can perform other operations!");
 }
 ();
}
static string ShowMessage(string x)
{
 string current = ("Current threadidfor{0}",);
 (3000);
 return ("{0},输入for{1}", current, x);
}
static void Completed(IAsyncResult result)
{
 ("Asynchronous completion!");
 //Get the delegate object and use the EndInvoke method to get the return result AsyncResult _result = (AsyncResult) result;
 Func<string, string> showMessage = (Func<string, string>) _result.AsyncDelegate;
 //End asynchronous operation and output ((_result));
}