Develop Reference

How to sync local data to server in Blazor WebAssembly-PWA?

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.

Unity PlayerPrefs not saving across re-installs on Android

I have a 'Money' PlayerPref, I'll give myself money, make it save, upon reinstalling the android APK, it deletes ALL the playerpref's, including owned objects ETC. please help.

Any data that is saved on an android device is associated to the application. When the application gets uninstalled, so does its data.
When an application is updated however, the data precists on the device and only the application gets updated.
To allow data to persist across devices or installs you need to use a remote server to store the data, such as Google's Saved Games Service.

You do not have to necessarily save your data in any of the clouds. ***
Save the data on the external sd card in custom folder
*** and access that data from the game everytime. Make sure to include the if(!data.null) exception handeling for security purpose.

How to use a Database from a Windows tablet UWP app?

I will soon be deciding on a project for my university course and I had one in mind which is going to be a windows tablet application, using the UWP tools in Visual Studio, as I want to develop skills in C# and the Mobile area.
However I will need to have a database behind my application to submit and retrieve data from. Is this a relatively "simple" and common task to do? I'm not looking for easy, I just want something that I can accomplish though without worrying too much over the basics.
My original thought was to have a database on my PC and then host it for my tablet to connect too, but that would require constant internet connection and for my PC to be hosting. After having done a little bit of research I came across something called SQLite, which people seem to think is a good local database to put into the device.
Having no experience with mobile applications though, I was curious as to how I would develop an application on my PC, and then put it onto the Windows Tablet, both using the same database? Would I need to duplicate the database between systems? Or would I write the code up on my PC and then test it on my Tablet?
Again this is an area i'm still new to, database 'hosting' and mobile applications. Maybe i'm just over thinking things, but just by asking the question I can already tell I sound clueless. My experience has been with small WPF applications, Console Applications and Websites.

I will need to have a database behind my application to submit and retrieve data from. Is this a relatively "simple" and common task to do?
I think the answer is yes. As you mentioned, SQLite is a good local database for you to use. Since there are guidance, samples, teach videos for SQlite with UWP, it should be simple and common task for you to do.
I was curious as to how I would develop an application on my PC, and then put it onto the Windows Tablet,
For this you need to Get started with Windows apps. After you finished developing the app on the PC, you can publish to windows store or Sideload your app package, then you can install the app on your tablet from store or through side loaded package.
Would I need to duplicate the database between systems?
The SQlite database is actually a database file with .db or other suffix saved on the local device. Whether need duplicate depend on where you put the database file on. Since UWP app is sandbox and have limitations for access the folder on the device. By default, all apps can access the following two locations, Application install directory and Application data locations. If you put the database file on Application install directory, once you install the app on one device, the database will exist on the install directory and you don't need copy. But this directory is read only means that if your database don't need update and read only you can use. For another location,Application data location there are LocalFolder,RoamingFolder and TemporaryFolder. If you put the database on LocalFolder it cannot be roamed and you need to manually copy or user a cloud server helper you save it for roaming.If you put the database on RoamingFolder it can roam pay attention it has some restrictions. More details please reference File access permissions. In my option, SQLite is a local database, which is using only for local data will be better, I don't recommend you to use it for roaming. If you need a roaming data base, a database on cloud or server side will be much better.

Having no experience with mobile applications though, I was curious as to how I would develop an application on my PC, and then put it onto the Windows Tablet, both using the same database?
You should get start from this document Intro to the Universal Windows Platform. I believe you'r familiar with C# language, you can use C# to develop UWP apps.
As you mentioned, you could use sqlite as local database in your app. You could use LiveSDk's APIs to synchronous database when you switch from PC to tablet.
Here's a sqlite sample in uwp for your reference.
The OneDrive Photo Browser sample shows you how to get data from cloud, it would be helpful to you.

Data Sync between local database and online database

I am developing a C# based window store app which has GUI developed using WPF.
The application's database is already on the Cloud through Windows Azure, but, I also want to have local copy of it through SQLite
Now, my question is:
How can I synchronize the data between Windows Azure and SQLite?

You can use Windows Azure Offline Sync. This tutorial may help you which states:
Offline support will allow you to interact with a local database when
your app is in an offline scenario. Once your app is online with the
backend database, you sync your local changes using the offline
features.
this video may also help support the tutorial

Implementing a desktop .NET application that can work offline.

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.