private async Task <IMobileServiceSyncTable <T> > GetInitialisedSyncTable <T>(string key, Expression <Func <T, bool> > query = null)
{
MobileServicePushFailedException pushFailedException = null;
var table = mobileService.GetSyncTable <T>();
var mobileServicesQuery = query == null
? null
: table.Where(query);
try
{
if (internetAccessIsAvailable)
{
await table.PullAsync(key, mobileServicesQuery ?? table.CreateQuery());
}
}
catch (MobileServicePushFailedException ex)
{
pushFailedException = ex;
}
if (pushFailedException != null)
{
string errorMessages = pushFailedException.PushResult
.Errors
.Aggregate(new StringBuilder(),
(s, a) => s.AppendLine(a.RawResult),
s => s.ToString());
await logger.LogExceptionAsync(pushFailedException, Constants.LOGGING_DATAKEY_PUSHERRORS, errorMessages);
throw pushFailedException;
}
return(table);
}
/// <summary>
/// Performs Simple Conflict Resolution reverting to server copy if mobile api update fails
/// </summary>
/// <param name="mspfe">MobileServicePushFailedException occured during sync</param>
/// <returns></returns>
private async Task SimpleConflictResolution(MobileServicePushFailedException mspfe)
{
if (mspfe.PushResult != null)
{
foreach (var error in mspfe.PushResult.Errors)
{
if (error.OperationKind == MobileServiceTableOperationKind.Update && error.Result != null)
{
//Update failed, reverting to server's copy.
await error.CancelAndUpdateItemAsync(error.Result);
}
if (error.OperationKind == MobileServiceTableOperationKind.Insert)
{
await error.CancelAndUpdateItemAsync(error.Result);
}
else
{
// Discard local change.
await error.CancelAndDiscardItemAsync();
}
Debug.WriteLine(@"Error executing sync operation. Item: {0} ({1}). Operation discarded.",
error.TableName, error.Item["id"]);
}
}
}
private async Task PerformOperationAndRetryIfUnauthorized(Func <Task> operation)
{
MobileServicePushFailedException pushFailedException = null;
try
{
await operation();
}
catch (MobileServiceInvalidOperationException ex)
{
if (ex.Response.StatusCode != HttpStatusCode.Unauthorized)
{
throw;
}
AccessToken = null;
}
catch (MobileServicePushFailedException ex)
{
pushFailedException = ex;
}
if (pushFailedException != null)
{
string errorMessages = pushFailedException.PushResult
.Errors
.Aggregate(new StringBuilder(),
(s, a) => s.AppendLine(a.RawResult),
s => s.ToString());
await logger.LogExceptionAsync(pushFailedException, Constants.LOGGING_DATAKEY_PUSHERRORS, errorMessages);
throw pushFailedException;
}
var accessTokenUpdated = await AccessTokenCouldBeMadeCurrent();
if (accessTokenUpdated)
{
await operation();
}
else
{
throw new UnauthorizedAccessException();
}
}
