/// <summary>
/// This is a wrapper for the asynchronous operation of querying bidi.
/// </summary>
/// <returns>IAsyncOperation so that this method is:
/// 1) awaitable in C#.
/// 2) consumed as a WinJS.promise on which we can then use .then() or .done().</returns>
public IAsyncOperation <string> GetInkLevelAsync()
{
return(AsyncInfo.Run(async(o) =>
{
// This allows the app to wait until a certain event is fired before continuing on.
// To prevent the waiting from locking up the entire computer, this is used in an async task.
AutoResetEvent waitHandler = new AutoResetEvent(false);
string queryString = "\\Printer.Consumables";
// Define the delegate for when OnBidiResponseReceived is invoked.
printerQueue.OnBidiResponseReceived += ((sender, responseArguments) =>
{
bidiResponse = ParseResponse(responseArguments);
// Set the waitHandler to signal that a response has been received.
waitHandler.Set();
});
// Send the query.
printerQueue.SendBidiQuery(queryString);
// Asynchronously wait for the the waitHandler to be set.
await Task.Run(() =>
{
waitHandler.WaitOne();
});
return bidiResponse;
}));
}
/// <summary>
/// Retrieve the ink level, and raise the onInkLevelReceived event when data is available.
/// </summary>
public void SendInkLevelQuery()
{
printerQueue.OnBidiResponseReceived += OnBidiResponseReceived;
// Send the query.
string queryString = "\\Printer.Consumables";
printerQueue.SendBidiQuery(queryString);
}