Crash when user attempts to purchase in-app product

Question

hi all,
I didn't use to get any crash reports before introducing in-app purchase. I have approx. 30 downloads a day and 5 crashes a day now which doesn't sound right.
Please could you help me find out why this is?
Here is the crash info. It seems like something goes wrong when the user presses the 'Buy Product button' and it looks like it's got something to do with the async/awaiting business. I'm very new to this and don't really understand.
Frame Image Function Offset
0 mscorlib.ni.dll System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess 0x0023a00e
1 mscorlib.ni.dll System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification 0x0000003a
2 mscorlib.ni.dll System.Runtime.CompilerServices.TaskAwaiter_1[[System.__Canon,_mscorlib]].GetResult 0x0000001c
3 BACanglais.ni.DLL BACanglais.WhatsIncluded+_Button_Click_d__2.MoveNext 0x000000b8
4 mscorlib.ni.dll System.Runtime.CompilerServices.AsyncMethodBuilderCore._ThrowAsync_b__0 0x00000036
my code behind the "Buy Product button" is as follows:
async private void Button_Click(object sender, RoutedEventArgs e)
// go to the buy product page
var listing = await CurrentApp.LoadListingInformationAsync();
var product1 =
listing.ProductListings.FirstOrDefault(p => p.Value.ProductId == "33333" && p.Value.ProductType == ProductType.Durable);
try
if (CurrentApp.LicenseInformation.ProductLicenses[product1.Value.ProductId].IsActive)
myVersionLine.Text = "FULL Version";
myUpgradeButton.Visibility = System.Windows.Visibility.Collapsed;
MessageBox.Show("You already own this product");
else
receipt = await CurrentApp.RequestProductPurchaseAsync(product1.Value.ProductId, true);
catch (Exception ex)
//MessageBox.Show(ex.ToString());
MessageBox.Show("Purchase did not take place");
thanks for your help. I'd hate to think that those 5 crashes a day are 5 potential buyers! what's strange is that no-one contacted me to say there was a problem.
anyone ran into a similar problem or has any idea?
many thanks!
cypripri

Answer 1

I can suggest to use the following strategy.
Define listing outside the Button_Click event
private ListingInformation listing = null;
and try to load the listing information before the user can tap on the button and you can enable the button after the listing has been loaded. For example, in the Loaded event of your page you can:
try
Task.Run(async () =>
listing = await CurrentApp.LoadListingInformationAsync();
}).Wait();}
catch { }
Button.IsEnabled = (listing != null);
In the Button_Click event verify that listing is not null, otherwise try to reload it.