I have an application that pulls a fair amount of data from different sources. A local database, a networked database, and a web query. Any of these can take a few seconds to complete. So, first I decided to run these in parallel:
Parallel.Invoke(
() => dataX = loadX(),
() => dataY = loadY(),
() => dataZ = loadZ()
);
As expected, all three execute in parallel, but execution on the whole block doesn't come back until the last one is done.
Next, I decided to add a spinner or "busy indicator" to the application. I don't want to block the UI thread or the spinner won't spin. So these need to be ran in async
mode. But if I run all three in an async
mode, then they in affect happen "synchronously", just not in the same thread as the UI. I still want them to run in parallel.
spinner.IsBusy = true;
Parallel.Invoke(
async () => dataX = await Task.Run(() => { return loadX(); }),
async () => dataY = await Task.Run(() => { return loadY(); }),
async () => dataZ = await Task.Run(() => { return loadZ(); })
);
spinner.isBusy = false;
Now, the Parallel.Invoke
does not wait for the methods to finish and the spinner is instantly off. Worse, dataX/Y/Z are null and exceptions occur later.
What's the proper way here? Should I use a BackgroundWorker
instead? I was hoping to make use of the .NET 4.5 features.
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