I need your help to manage an issue with my C# program. I wrote a GUI that allows the user to manage a lot of data stored in a SQL Server database. Everything works fine but I want to be sure that the application works even when the server is down (for a generic issue).
My plan is to have a local database (e.g. *.mdf database used in Visual Studio) and update it every time the GUI is able to connect to the online SQL Server database.
What do you think? Is there something similar to a procedure or do I need to do it manually (create a .mdf file, check the online version, write the changes etc.)?
Apart from the comments noting that this may not be a good idea (which I agree):
Most of the work must be done manually. If you have a DB model within your application (like when using entity framework) it could be that it can create the DB structure in the local file. Most of your data will need timestamps to determine when they were changed the last time.
The Microsoft Sync Framework might utilize you but I have not used it personally. Look here http://msdn.microsoft.com/en-us/library/bb902854(v=sql.110).aspx
Related
I have two sql servers installed on my computer (SQL2008 EXPRESS) and also SQL2008 that comes with the specific software that we are using.
I need to make a service that runs all the time and at a specific time updates the non existing records in the SQL2008 EXPRESS from SQL2008.. can you suggest a way of doing this?
Currently the best thing I got is making a local copy in excel file, but that will result 365 excel files per year which I dont think is a good idea :)
p.s. sorry if my english is bad :)
You don't have to hand-craft your own software for that. There are 3rd party tools like OpenDbDiff or RedGate dbdiff to do that. These tools generate the differential sql that you can apply on your target database.
I'm confused when you mention Excel. What would Excel have anything to do with moving data from one SQL database to another?
The short answer is, if you need a C# service, then write a C# service that copies the data directly from one database to the other. The problem that you are trying to solve is not very clear.
Having said all that, and with my limited understanding of the problem, it sounds like what you need is a SQL job that is scheduled to run once a day that copies the data from one server to the other. Since it sounds like they are on separate instances, you'll just need to set up a linked server on either the source or destination database and either push or pull the data into the correct table(s).
EDIT:
Ok, so if a windows service is a requirement, that is perfectly acceptable. But, like I mentioned, you should forget about Excel. You wouldn't want to go from SQL->Excel->SQL if you have no other reason for the data to exist in Excel.
Here is some information on creating a windows service:
Easiest language for creating a Windows service
Here is a simple tutorial on accessing SQL in C#: http://www.codeproject.com/Articles/4416/Beginners-guide-to-accessing-SQL-Server-through-C
If you want a more formal solution (read: data access layer), I'd point you toward Entity Framework. The complexity of the project will probably be the driving factor on whether you just want to do SQL statements in your code vs. going with a full blown DAL.
Is it possible to achieve this?
Download/fetch data from the database then save locally to a Windows Mobile app for later use (without internet connection).
Make changes to the database locally.
Upload the changes of the local database to update the database from the server manually.
I am thinking about a sync function but I am using an Oracle Database on the server and Oracle DB and SQL Server Compact doesn't support syncing with each other naturally.
Sure this is completely possible, but you are going to need to write the syncing feature yourself unfortunately. You might be able to incorporate this, but as of now there is no bolt-on solution for you, so you would need to add the syncing features.
Happy coding!
Please read about the ADO.NET technology.
It was made for implementation of your scenario - maintaining of disconnected cache of server data.
For example look at this article
And here is more specific example -> Disconnected Architecture in ADO.NET
Here's a great walkthrough from Microsoft on doing exactly this:
Walkthrough: Creating an Occasionally Connected Smart Device Application
Note that it was reported that this technique is not 100% reliable, meaning it can "forget" to post the latest data.
To get around this, you can add a TimeStamp DateTime field to each table that stores the time the latest data was written or updated, then modify your queries to only pull/push the latest records.
In my application programming experience, I have always worked with a SQL Server (or Access) database on the back end that stores application data. I'm now looking at some business requirements that work with data that would fit well in a relational database, but they require it to be stored in a single, portable, custom file that the application will create, and load from. I know it's a very common concept for an application to save off a single file or document that it can later load and continue to work on, but I'm not sure how to achieve this with complex data. Encrypting xml comes to mind, but that would be very slow to work with or potentially eat up a lot of memory if I had to load it all back into objects first. What are some options?
I recommend you use a SQLLite or Firebird embedded database. There are other options as well. They support single-file usage and will give you a clear upgrade path for future versions of you schema (upgrade SQL scripts).
I did not understand how encryption plays into this.
When running in a .NET environment I think that SQL Server Compact is worth looking into. It is basically a mini SQL Server that doesn't have to be installed and configured as a service, but instead is an dll that you reference. You can use normal data access tools like linq-to-sql and entity framework.
SQLite comes to my mind. Its a single file based DB. Here is a link to convert SQL server databases to SQLite. Also check out Using SQLite in your C# Application
I am in the midst of writing a small program (more to experiment with vs 2010 than anything else)
Despite being an experiment it has some practical use for our local athletics club.
My thought was to access the DB (currently online) to download the current members and store locally on a laptop (this is a MS sql table, used to power the club's website).
Take the laptop to the event (yes there ARE places that don't have internet coverage), add members to that days race (also a row from a sql table (though no changes would be made to this), record results (new records in 3rd table)
Once home, showered and within internet access again, upload/edit the tables as per the race results/member changes etc.
So I was thinking I'd do something like write xml files locally with the data, including a field to indicate changes etc?
If anyone can point me in a direction I would appreciate it...hell if anyone could tell me if this has a name, I'd appreciate it.
Essentially what you need is, in addition to your remote data store, a local data store on your desktop. You could then write your code by hand to sync the data stores when you go offline / online, or you could use the Microsoft Sync framework to handle it for you.
I've personally used the Sync framework on a number of projects and once you get used to the conventions, it's pretty easy to use.
If a local storage format is what your after. SQLite is one option. You can copy your tables from the server to your local SQLite db.
You could also save your data to files, but XML is a horrible format for doing this. You'll probably want to use YAML or JSON instead.
You may want to take a look at SQL Server Compact -- it provides some decent capabilities with synchronizing back with the mothership SQL server.
If you're using MS SQL Server for production, and you only need to work offline on your personal computer, you could install MS SQL Server Express locally. The advantage here over using a different local datastore is that you can reuse your schema, stored procedures, etc. essentially only needing to change the connection string to your application (which you could run locally too through Visual Studio). You would have to write code to manually sync your online and offline db instances, but since it's a small application, it may be reasonable to just copy the entire database from production to local and then from local to production when you get home (assuming you're the only one updating the db, and wouldn't be potentially wiping out any new records entered in production while you were at the event).
Google Gears http://gears.google.com/ is intended if your app is a web app (which I didn't quite get what it is from your description)
How do i create a db file in C#? a friend told me it was in the toolbox and not to use sqlite. I dont see anything that could be it, nor what it is called. google didnt help:(
Could it be...
SQL Server Compact Edition – A lightweight, in-process database engine designed to run on devices and desktops and is geared toward local data storage. Compact Edition includes a subset of SQL Server 2005 data types and shares common elements of the Transact-SQL (T-SQL) language with the data service engines.
There is no file-based database provider built in to c# or the .NET Framework. There are of course pre-existing connectors for using SQL Server (which includes SQL Express), but if you need a fully functional RDBMS that is file-based, you need to use something like SQLite or Firebird (also a fan of VistaDB, not free or open source but VERY solid and pretty affordable).
On the Add New Item menu: "Service-based Database" or "Sql Server Database" if it is an asp.net application. I am sure your friend meant it as "create a sql express db file in Visual Studio".
That said, if you wanted to fill an empty database, with tables that correspond to a c# model, you could create a linq2sql model, and use its CreateDatabase to do that for you :)
You might want to check this http://quickstarts.asp.net/QuickStartv20/aspnet/doc/data/vwd.aspx (visual web developer link, but it applies).
For a full/in-depth explanation of how SQL express can be used with a semi file based approach check and its limitations:
http://www.databasejournal.com/features/mssql/article.php/3704171/SQL-Server-2005-Express-Edition---Part-8---XCopy-Deployment.htm
Perhaps you might try Microsoft LocalDB.
It is file based but uses a low level SQLExpress Installation to host it.
If you are using Visual Studio or Web Developer Express, there are indeed ways to easily create a MS SQLExpress database. Just go to Add New Item... and it should be one of the available file types.
Keep in mind you have to have installed either Microsoft SQL Express Edition (free, as in beer!) or Microsoft SQL (very un-free!, in all senses). If you haven't done this, you don't get the option of creating a database file so easily. If you have got it yet, you can get it here.
As other answerers have mentioned, strictly speaking this is NOT a C# feature. MS SQL and it's derivatives, are database applications, much like Oracle, MySQL, or PostgreSQL. It's just that Microsoft Visual Studio makes using the Microsoft database product very easy by default. Differentiating between C#, Visual Studio, and any database programs will probably get you better answers, faster, no matter where you ask. :)
Every database has a file system in some binary format more than likely custom and uses a cache to control the flow of the database(s) lifetime.
If you create a database system, you will need some type of cache because you only want to read from the file if the cache has already released it.
If you have 1000 clients tapping into the same db, you certainly don't want to read/write to the file for each client request, so you want to manage a queue of clients and run it against the cache so that the cache knows not to release the db after its time span for lifetime is reached put to rather update the time span, therefore, not having to reload the file, if disposed and queued again, until the queue referencing the db object is empty.
Creating a well designed cache it used by all rdbms's so that duplicate objects are not created and files are not reloaded if not need be.
You can use
FileDB - A C# database to store files
http://filedb.codeplex.com
There is a MVC Example in the source that allows you to upload files and also has drag and drop support.
It then saves it into just one file in a location that you specified.
Like this:
private string pathDB = #"C:\CMS-MVC\Parts\FileManager\filedb-19055\trunk\MvcTest\Data\MvcData.dat";
That one file will store all of your files in that one "container".
You are mistaken. Databases are not developed in C#. Databases are built using a database system such as Oracle, MS SQL Server, MySQL, and numerous others.
Once you build a database using one of the above providers, you can then perform actions on the database using your programming language of choice (in your case C#) to get data out of and put data into it.