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)
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.
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
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.
I have deployed plenty of software to my clients. Mostly are Window Forms applications.
Here is my current practice.
Manually install SQLExpress and SQL Management Studio to each client PC.
Then use ClickOne to install the code from the server.
When there is a changes in code, I will use ClickOne to deploy -(NO PROBLEM with this step)
But when there is a change in a database column, what do I do?
I have even tried writing a database update script. Each time the program starts, it will read through the .sql update file and run them if the database exists. This solves the problem of updating the database columns, but it does not help in my DEBUGGING work when my customer complain there is a wrong data. At that point, I have to personally go to their site to check it out.
I find it difficult to have the database installed on the client PC as it make my debugging work very very difficult. I am thinking about moving my client database to a host on an Online server. But that then comes with these constraints:
What if the internet is down?
What if my customer has no internet?
Could you help to advise me? Is this a common problem faced by developer? What is the common practice out there? Does Window Azure or SQL CE help?
Depending on the data I would recommend using SQL CE.
If the data isn't too much, speed is not the primary goal (CE is slower than Express) and you don't need DB-Features not supported by CE (e.g. stored procedures) it is the better choice IMHO, because:
The client does not need to install a full SQL server (easier installation/deployment)
You do not have problems with multiple SQLExpress instances
Your SW doesn't need to worry if there even is a SQL instance
Less resources used on the client side
Additionally the clients could send you their SQL CE DB-File for inspection and you do not need to go to their site.
It is also relativly easy to implement an off site sync with SQL CE and MS Sync FW.
Installing one database per client PC can be tricky. I think you have a decent handle on how to deal with the issue currently. It seems like the real issue you are currently facing is debugging. To deal with this, there are a couple ways you could go:
Have the customer upload their copy of the database back to you. This would provide you with the data they have and you could use it with a debug copy of your code to identify the issues. The downside is that if the database is large it might be an issue transferring it.
Remote onto the customer's machine. Observe the system remotely using something like CoPilot. That way you could see what is happening in its natural environment.
There are probably other ways, but these are a couple of good ones. As for using an online database, this is an option but it brings its own set of issues with it. You mentioned a couple. As for Azure, that is cloud-based (online) so the same issues will apply. SQL CE won't help you any more than your current installation does.
Bottom line is that I would recommend you look into the ways to fix your one issue (as listed above) instead of creating a whole new set of issues by moving to an Internet-based solution. I would only recommend moving to the Internet if it was addressing a larger business need (for example, mobility). Doing the same thing you have been doing only online will probably just make life harder.
To recap the comments below since they are so pertinent to the issue, if you are choosing between file-based databases that don't need to be physically installed on the machine, your best choices are probably between SQLite and SQL CE. Microsoft supports SQL CE better but it is a larger package and has less features than the trim SQLite. Here is a good discussion on the differences:
https://stackoverflow.com/questions/2278104/sql-ce-sqlite-what-are-the-differences-between-them
However, the issue gets more complicated when you start looking at linq2sql since that is designed for SQL server. Microsoft does not support SQL CE with linq2sql out of the box, although there is a work-around that will get it to work:
http://pietschsoft.com/post/2009/01/Using-LINQ-to-SQL-with-SQL-Server-Compact-Edition.aspx
SQLite is not supported at all with linq2sql but there is a way to use linq to talk with SQLite:
LINQ with SQLite (linqtosql)
This library also supports other common databases including MySQL and Firebird.
You could use the SQLCMD utility to execute the change script, as mentioned in this related question
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.