private void Download2Callback(IAsyncResult ar)
{
var localState = (State)ar.AsyncState;
string data2;
try
{
data2 = _downloadFromInternet2.EndDownload(ar);
}
catch (Exception exception)
{
localState !.TaskCompletionSource.TrySetException(exception);
return;
}
bool readyToWrite;
lock (localState)
{
localState.Data2 = data2;
localState.HasData2 = true;
readyToWrite = localState.HasData1 && localState.HasData2;
}
if (readyToWrite)
{
SaveResults(localState);
}
}
// Very old-school implementations use an IAsyncResult by Jeffrey Richter from an old MSDN article:
// https://docs.microsoft.com/en-us/archive/msdn-magazine/2007/march/implementing-the-clr-asynchronous-programming-model
// This example code uses the much simpler Task/TaskCompletionSource approach introduced in .NET 4.0.
public IAsyncResult BeginDownloadAndSave(AsyncCallback callback, object state)
{
var tcs = new TaskCompletionSource <object>(state);
_downloadFromInternet.BeginDownload(ar =>
{
string data;
try
{
data = _downloadFromInternet.EndDownload(ar);
}
catch (Exception exception)
{
tcs.TrySetException(exception);
return;
}
_saveToDatabase.BeginSave(data, ar =>
{
try
{
_saveToDatabase.EndSave(ar);
}
catch (Exception exception)
{
tcs.TrySetException(exception);
return;
}
tcs.TrySetResult(null);
}, null);
}, null);
return(tcs.Task);
}
