BillingConnection for Google Play

BillingConnection.cs

public class BillingConnection : Java.Lang.Object, IServiceConnection
{
    private TaskCompletionSource<bool> _connectSource;

    public IInAppBillingService Service
    {
        get;
        private set;
    }

    public async Task Connect()
    {
        var intent = new Intent(BillingConstants.BillingIntent);
        intent.SetPackage(BillingConstants.BillingPackageName);
        var context = Application.Context;
        int intentServicesCount = context.PackageManager.QueryIntentServices(intent, 0).Count;
        if (intentServicesCount != 0)
        {
            var source = 
                _connectSource = new TaskCompletionSource<bool>();
            context.BindService(intent, this, Bind.AutoCreate);
            await source.Task;
        }
        else
        {
            throw new Exception($"Service {BillingConstants.BillingIntent} not found!");
        }
    }

    public void Disconnect()
    {
        Application.Context.UnbindService(this);
    }

    public void OnServiceConnected(ComponentName name, IBinder service)
    {
        try
        {
            Service = IInAppBillingServiceStub.AsInterface(service);

            int response = Service.IsBillingSupported(BillingConstants.ApiVersion, Application.Context.PackageName, BillingConstants.ItemTypeInApp);
            var source = _connectSource;
            if (response == BillingConstants.ResultOk)
            {
                if (source != null)
                    source.TrySetResult(true);
            }
            else
            {
                if (source != null)
                    source.TrySetException(new Exception("Billing not supported!"));
            }
        }
        catch (Exception exc)
        {
            var source = _connectSource;
            if (source != null)
                source.TrySetException(exc);
        }
    }

    public void OnServiceDisconnected(ComponentName name)
    {
        Service = null;
    }
}