Azure / Xamarin - SyncContext.InitializeAsync Deadlock

Question

I have a Xamarin.Forms App which use Azure App Service with SQLLite Offline Sync. When calling SyncContext.InitializeAsync a deadlock appears and the function InitializeAsync never finished.

In this Thread in found the solution: Azure/Xamarin Mobile App Hangs at SyncContext.InitializeAsync

This works:

 System.Threading.Tasks.Task.Run(() => this.IDataProvider.IMobileServiceClient.SyncContext.InitializeAsync(localStore, _syncHandler)).Wait();

This not:

await this.IDataProvider.IMobileServiceClient.SyncContext.InitializeAsync(localStore, _syncHandler);

Whole function:

   public override async System.Threading.Tasks.Task Init()
        {
            string storePath = System.IO.Path.Combine(Microsoft.WindowsAzure.MobileServices.MobileServiceClient.DefaultDatabasePath, localStoreName);
            Microsoft.WindowsAzure.MobileServices.SQLiteStore.MobileServiceSQLiteStore localStore = new Microsoft.WindowsAzure.MobileServices.SQLiteStore.MobileServiceSQLiteStore(storePath);

            localStore.DefineTable<CPM.Recruitment.Mobile.Freelancer.DataObjects.Entities.Promoter>();

            System.Threading.Tasks.Task.Run(() => this.IDataProvider.IMobileServiceClient.SyncContext.InitializeAsync(localStore, _syncHandler)).Wait();
            //await this.IDataProvider.IMobileServiceClient.SyncContext.InitializeAsync(localStore, _syncHandler);

            _promoters = new Azure.AppService.DataObjects.Client.Sync.List<CPM.Recruitment.Mobile.Freelancer.DataObjects.Entities.Promoter>(this, this.IDataProvider.IMobileServiceClient.GetSyncTable<CPM.Recruitment.Mobile.Freelancer.DataObjects.Entities.Promoter>());
        }

But why? I dont want to use Wait();

Amor Amor · Accepted Answer · 2017-04-12T05:18:39

The differences between await and Wait method are:

await means the current task will be executed in a separated thread asynchronously and the calling thread won't be blocked. If the calling thread is UI thread. the UI thread will continue to run other operations.

Wait method are synchronization method. It causes the calling thread to wait until the current task has completed. If the calling thread is UI thread, UI operations will be blocked.

It seems that a deadlock will be caused if you use await to run the task which will not block UI thread.

Azure / Xamarin - SyncContext.InitializeAsync Deadlock

1 Answers