Question

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.

Answer 1

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);
}