CODEWITHSUNDEEP
c#asynchronous
robertpnl
robertpnl

Reputation: 704

Using System.Func anonymous and the return object with callback function

Maybe simple question but how can I get the return object of a asynchronously System.Func?

Consider this:

private void Start(String a)
{
    System.Func<String, objectA> callasync = delegate(String strA)
    {
        return bla(stra);  // Which return a objectA
    }

    callasync.BeginInvoke(a, callback, null);
}

private void callback(IAsyncResult ar)
{
    // Here I want the objectA but how ??
}

With callback function, I didn't have the delegate signature. And of course, i can create a delegate in scope of the class but maybe is there a solution to read the return value in the callback function.

Thank.

Upvotes: 0

Views: 979

Answers (2)

Sven
Sven

Reputation: 22693

When you use BeginInvoke on a delegate, the IAsyncResult of passed to the callback will be an instance of the AsyncResult class. From that you can get an instance of your delegate and call EndInvoke on it.

private void Start(string a)
{
    Func<string, objectA> d = strA => bla(strA);

    d.BeginInvoke(a, Callback, null);
}

private void Callback(IAsyncResult ar)
{
     AsyncResult asyncResult = (AsyncResult)ar;
     Func<string, objectA> d = (Func<string, objectA>)asyncResult.AsyncDelegate;
     objectA result = d.EndInvoke(ar);
}

Upvotes: 1

Brian Dishaw
Brian Dishaw

Reputation: 5825

You could also do something like this (not written in IDE, may contain errors)

  private Func<String, objectA> _callDoWorkAsync = DoWork;
  private static string DoWork( objectA strA )
  {
     return bla( strA );
  }

  private void Start( String a )
  {
     _callDoWorkAsync.BeginInvoke( a, callback, null );
  }

  private void callback( IAsyncResult ar )
  {
     objectA strA = (objectA) _callDoWorkAsync.EndInvoke( ar );
  }

Upvotes: 0

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