I need to create a desktop WPF application in .NET.
The application communicates with a web server, and can work in offline mode when the web server isn't available.
For example the application needs to calculate how much time the user works on a project. The application connects to the server and gets a list of projects, the user selects one project, and presses a button to start timer. The user can later stop the timer. The project start and stop times need to be sent to the server.
How to implement this functionality when the application is in offline mode?
Is there are some existing solution or some libraries to simplify this task?
Thanks in advance.
You'll need to do a couple of things differently in order to work offline.
First, you'll need to cache a list of projects. This way, the user doesn't have to go online to get the project list - you can pull it from your local cache when the user is offline.
Secondly, you'll need to save your timing results locally. Once you go online again, you can update the server will all of the historic timing data.
This just requires saving the information locally. You can choose to save it anywhere you wish, and even a simple XML file would suffice for the information you're saving, since it's simple - just a project + a timespan.
It sounds like this is a timing application for business tracking purposes, in which case you'll want to prevent the user from easily changing the data. Personally, I would probably save this in Isolated Storage, and potentially encrypt it.
You can use Sql Server Compact for you local storage and then you microsoft sync framework to sync your local database to the server database. I recommend doing some research on the Microsoft Sync Framework.
Hello all I implemented this application I've created my own off-line framework
based on this article and Microsoft Disconnected Service Agent
DSA
I've adapted this framework for my needs.
Thank you for all.
you can use a typed or untyped dataset for offline-storage.
when online (connected to internet) you can download the data into a dataset and upload it back to the database server. the dataset can be loaded from and saved to a local file.
Related
I want to building a Blazor WebAssembly Progressive Web App, that can run offline.
I began Blazor this morning, and I'm just trying to get the hang of it.
To begin I want to do something like keep.google.com. You can work on you notes offline, on different devices, and when the connection is re-established, all notes are synchronized in the background with the server.
My idea is to have simple notes on a server, with an id, title and a message. These notes can be displayed and added/modified from the client. Since I want the application to work offline, I want the synchronization process to be as follows:
The fist time visiting the website, all notes are fetched from the server,
When notes are added/modified, they are saved on the server,
If connection is lost, notes can still be read and added/modified localy,
When the connection is re-established, the modifications are saved to the server,
Periodically or after pressing a button, sync is done between client and server to fetch new data present on the server.
I think the way to do this is to have a copy of the database localy. Client do modification on the local database and periodically/after pressing a button/when connection is re-established, I sync local database with server database.
I'm sure there is an official and easy solution to do that. I followed the CarChecker example from Microsoft, but they used the IndexedDB in javascript to do that (23min13 in the official tutorial video).
Do you know a .NET solution/tutorial/service that store data locally, and sync in the background with the server ?
I wrote a Blazor WebAssembly PWA with similar technical requirements. There is certainly more than one way to accomplish this but the steps I used are as follows:
I used sqlite on the client side to persitist the data locally. The simplest way to make that persist-able with the ability to use Entity Framework is to use the SqliteWasmHelper nuget package. https://github.com/JeremyLikness/SqliteWasmHelper
On startup and/or when online I fetch the necessary data and insert it into the local sqlite database.
The user can make changes and I save that to the local sqlite DB and mark it as ready to be synced.
I have a background service with a timer which executes on a configurable interval and grabs the local data marked to be synced and calls the API on the server to save the data to a SQL Server database. Of course I check to see that the user is online before attempting the sync.
I use Javascript to determine whether the device is online. I can provide that to you if you need but you should be able to google it.
I have an application update checker based on this method which works pretty well: https://whuysentruit.medium.com/blazor-wasm-pwa-adding-a-new-update-available-notification-d9f65c4ad13
I hope that helps. I'm happy to provide more detail if you like.
In my C# WPF Core application, using OLEDBConnection, I am able to read data from my Access database without being connected to the same network which contains my SharePoint site. My objective is to write data to the Access DB while not connected to the network, then synchronize at a later point which I am connected to the network. Below is the AccessViolationException caused by Office 365 trying to connect.
The issue is not the OLEDBConnection. I am able to read successfully from the DB and my SQL is generated successfully on the updates. How can I work around this Sharepoint automatic login functionality in order to write to my access DB (but not synchronizing to the master DB)?
The problem here is you attempting to use oleDB to connect to a local Access database, but that database is NOT really ONLY local, but is connected and synced to SharePoint. And the logon on parts, the sync parts, and the off line mode, the on-line mode is ALL PART of Access and NOT just oleDB.
In other words:
You need to write your application in Access if you want to free-load off of all those fancy extra parts like the SharePoint logon, and the Access sync to tables and all that fancy stuff that is part of Access.
If you going to use .net? Then the .net application has to hit the SharePoint web services and use + consume the SharePoint lists directly - not have Access do all that extra cool work. .net has all of the abilities to hit SharePoint, and the web service calls can be REST, but I think most are in fact SOAP calls. (but SOAP and a WSDL for SharePoint is well documented and supported).
If you need a off-line, then on-line sync system? Then you have to roll your own, or use the depreciated sync framework for.net (it is depreciated, but can still be used. And there is/are sync providers for SharePoint. So, you could still have a local accDB (Access data file), but the data tables would not be linked to SharePoint. Your .net application will have to do the sync stuff.
You trying to hit the tables via oleDB, but you THEN want all that SharePoint logon, and all that VERY WAY COOL SharePoint sync stuff built into Access (which is NOT just part of the database engine and oleDB, but is bits and parts that belong to Access.).
You could consider and attempt to automate a WHOLE running copy of Access. But then again, you would not be using oleDB anymore, but in fact just like you can create a instance of Word, or Excel or say Outlook in .net? You would thus be creating a full running copy of Access.
Keep in mind that Access as a COM object does not really correctly expose the off-line, on-line and sync options with a nice set of clean methods and properties. I know this to be the case, since even from VBA, you can't really control the off-line mode vs the on-line mode. What you can do is "test" and "know" if you are currently disconnected. You can then execute a refresh tables command.
VBA:
DoCmd.RunCommand acCmdRefreshSharePointList
However, the above will then attempt to refresh, and if the user is off line, the app will remain off line, but WILL tell the user. The user is THEN given this option:
So, they have to click on this option. Once they then re-connect, then they will see this:
So, the above acCmdRefreshSharePointList ONLY really triggers a full refresh (and sync) of data AFTER the user has cliced on the UI above. Unfortunately, to my knowledge the UI is the the ONLY way to for the user to deal with the SharePoint connected, or not (you can test/check in VBA, but you can't control it). Once the user as per above has re-connected, then then you can force a refresh as per above command, but it really don't help a lot, since you can't toggle or control the off/line or on/line mode from VBA (and thus via COM object automation from .net you can't either).
So the the meat and parts you need to control the logon etc. is part of Access and NOT part of the oleDB object model.
As noted, even the Access model does not expose the control of the off/line and on-line mode in a useful way. But it better then what you have from .net.
If you using .net? The as noted, hit the SharePoint web services to inter-act with the lists, and if you need a local off-line mode, then you have to roll your own sync system, or use the .net sync framework.
After using Azure Mobile Services a year ago, I decided to get back to mobile development but Microsoft changed a lot in their offer and I'm actually struggling to set my project up.
My goal is to create a service whith these features:
.NET backend preferred over the Javascript one (I don't like callbacks :))
SSO (Facebook, Twitter, Google+, Windows Live)
SQL Database (I really need relations, and I already have a T-SQL schema)
Push Notifications (just to Windows and Android for now and with unlimited custom channels so that I can have one channel for each user and avoid dealing with notifications' logic)
Monthly scheduled jobs to update database from an external JSON API and to remove old entries
Mobile Client (with a shared Xamarin library to handle all the data-related stuff and WUP + Android support)
Web Client (I don't have a Mac so I can't build and publish the iOS version, so a web app may be needed as a temporary replacement)
What I did was to:
Open Azure Preview Portal link
Click on New => Web + Mobile => Mobile App
Set the Resource Group with all the needed plans
Added a Data Connection to a newly created SQL Database
Added a Notification Hub with settings for GCM and WNS
Added Mobile Authentication with settings for Microsoft Account, Facebook, Twitter, Google
Created the schema for my SQL Database
Before going on, I'm not sure that this was the correct workflow but documentation is pretty confused and the Get Started sections just discuss about code and not how to properly setup the service and have it running, so I just did the same basic things that I would've done with the old Mobile Service, plus dealing with the SQL Database instead of the NOSQL one.
Now it comes the issue: I have no idea on how to move next, and even the Quickstart projects (both server and client) are not helpful (they're the old TodoItem sample working with the Mobile Service).
The first thing that I wanted to do was to create the Scheduled Job because I actually need to fill the database with the external data before moving forward.
The only thing close to what I need is the WebJob, but I can't schedule it yet and it requires me to upload an exe file while I'd like to be able to write my C# code directly to the server (being able to remotely debug it).
An alternative may be to create a Compute Instace and write an endless loop doing what I need, but this will force me to manually deal with the SQL Database inside the Mobile App Service.
Another issue is related to the SQL Database. As I already wrote, the Quickstart seems to work with the NOSQL included in the old Mobile Service, meaning that I don't have a direct connection to my SQL Database, while I'd like to be able something like
App.MobileService.GetTable<MyTable>()
Plus, having 10 tables, I'd also like to have a way to map them automatically (like NetBeans does for JavaEE projects).
So the question is: what's a good (or the best) workflow to get everything working as I need it or, at least, close to how I need it?
(I know that answers may be opionion-based but they still may be useful since Microsoft's documentation is not complete)
If you have an existing database, you could use Entity Framework Code First to Existing Database. That will generate the C# classes for you.
The database that you create when you add a Data Connection to your Mobile App is an Azure SQL Database by default--I'm not sure why you thought it was NoSQL?
Once you have done this, you can query your tables from the Azure Mobile Apps client SDK. For instance, in Xamarin, the quickstart project does queries as follows (see https://github.com/Azure/azure-mobile-services-quickstarts/blob/MobileApp/client/xamarin.android/ZUMOAPPNAME/ToDoActivity.cs#L126).
var list = await toDoTable.Where (item => item.Complete == false).ToListAsync ();
Finally, regarding your question on WebJobs, you can actually schedule it. See https://azure.microsoft.com/en-us/documentation/articles/web-sites-create-web-jobs/#CreateScheduledCRON for more information. Even though you Web Deploy your webjob target, you can still remote debug it. See this blog post for information: http://www.bursteg.com/remote-debugging-azure-webjobs-attach-a-debugger-from-server-explorer/
I'm going to develop a POS system for medium scale company
and the requirement for me is to make all data on time for all of their branches
while in my mind, move the server from local to web would solve this problem
but, i never done any online server for window application
may i know what is the best option for use as secure database ?
such as SQL can handle this well ?
i tried to google but all of the result return is not what i want
may i know what will you do when you facing this problem ?
my knowledge on coding is just VB and CS
also SQL for database
i would like to learn new if there is better option
i hope it is impossible to access by anonymous and it is store secure at back-end only
What you probably want to do is create a series of services exposed on the internet and accessed by your application. All database access would be mediated by these services. For security you would probably want to build them in WCF and expose them through IIS. Then your Windows application would just call these services for most of its processing.
If you design it properly you could also have it work with a local database as well so that it could work in a disconnected manner if, for example, your servers go down.
Typically you don't move the server off of the site premises.
The problem is that they will go completely down in the event your remote server is inaccessible. Things that can cause this are internet service interruption (pretty common), remote server overloaded (common enough), basically anything that can stop the traffic between the store location and your remove server will bring them to their knees. The first time this happens they'll scream. The second time and they'll want your head due to the lost sales.
Instead, leave a sql server at each location. Set up a master sql server somewhere. Then set up a VPN connection between the stores and this central office. Finally, have the store sql boxes do merge replication with the central office. Incidentally, don't use the built in replication, but an off the shelf product which specializes in replicating sql server. The built in one can be difficult to learn.
In the event their internet connection goes dark the individual stores will still be able to function. It will also remain performant as all of the desktop app traffic is purely to the local sql box.
Solving replication errors is much easier than dealing with a flaky ISP.
I would recommend you to check Viravis Platform out.
It is an application platform that also can be used just as an online database for any .NET client with the provided SDK. It has its own generic windows and web clients and some custom web solutions for some specific applications.
You may be using it as a complete solution or as a secure online database backend.
I have a datalogging application (c#/.net) that logs data to a SQLite database. This database is written to constantly while the application is running. It is also possible for the database to be archived and a new database created once the size of the SQLite database reaches a predefined size.
I'm writing a web application for reporting on the data. My web setup is c#/.Net with a SQL Server. Clients will be able to see their own data gathered online from their instance of my application.
For test purposes, to upload the data to test with I've written a rough and dirty application which basically reads from the SQLite DB and then injects the data into the SQL Server using SQL - I run the application once to populate the SQL Server DB online.
My application is written in c# and is modular so I could add a process that periodically checks the SQLite DB then transfer new data in batches to my SQL Server.
My question is, if I wanted to continually synchronise the client side SQLLite database (s) with my server as the application is datalogging what would the best way of going about this be?
Is there any technology/strategy I should be looking into employing here? Any recommended techniques?
Several options come to mind. You can add a timestamp to each table that you want to copy from and then select rows written after the last update. This is fast and will work if you archive the database and start with an empty one.
You can also journal your updates for each table into an XML string that describes the changes and store that into a new table that is treated as a queue.
You could take a look at the Sync Framework. How complex is the schema that you're looking to sync up & is it only one-way or does data need to come back down?
As a simply solution I'd look at exporting data in some delimited format and then using bcp/BULK INSERT to pull it in to your central server.
Might want to investigate concept of Log Shipping
There exists a open source project on Github also available on Nuget. It is called SyncWinR, it implements the Sync Framework Toolkit to enabled synchronization with WinRT or Windows Phone 8 and SQLite.
You can access the project from https://github.com/Mimetis/SyncWinRT.