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create setup file and let user choose where to save database

with very short words,
i have created a project which contains database using sql server; and of course i want the database to be separated or in some place away from drive C so i want to let the user choose where to save his database when he install program to be able to move it if necessary and not to lose data all the time because employees are not well-trained using computers
or if possible make whole program portable
can somebody help me or send me link with clear explanation because i couldn't find something helpful
thnx in advance

It's very easy to create a database dynamically using SQL Server Compact Edition (SQL CE) which is a compact relational database that is very easy to configure and deploy from your application dynamically. It sounds like a viable solution for the environment you describe. Rather than recycling code I found some good beginner resources for you:
Getting Started with SQL Server Compact Edition
Create a SQL Server Compact Edition Database
Create a Table in SQL Server Compact Edition

Switching from using SQL Server Express to SQL Server Compact

So far I have been using SQL Server Express on my desktop application even though usually the server is only used by that single application, by the single user, on the same single machine. This always seemed a bit silly to me since the full-on server is rather heavy.
Then I found out that there is something called SQL Server Compact. Thing is, my application is already rather large. So my question is that if I wanted to change to SQL Server Compact, what kind of changes to my code are we talking about (using C#)?
Mainly I'm wondering if I can access the Compact -version in the same manner as I can access the Express one, which is using ADO.NET and pointing it towards localhost\sqlexpress. So would it be possible to create another instance with the Compact and just point my application to that, or is it used in a completely different manner?

For a standalone desktop product it is certainly a lightweight option to consider over SQL Express.
However there are differences between the two to be aware of other than just connection strings. For example SQL CE does not support stored procedures, user-defined functions, or triggers. Additionally it does not support the full range of datatypes that Express supports. On a technical level it also runs in process with your application.
Another consideration is that while SSMS will work with SQL CE databases, it's not as fully featured as it is with SQL Express. There are however a whole raft of good tools out there for filling these gaps. Take a look at Erik Jensen's blog for a good overview.
Everything SQL Server Compact
Also check out his tool for migrating SQL Express databases to SQL Compact:
How to Migrate/Downsize a SQL Server database to SQL Server Compact 4.0 (and 3.5)
Finally take a look at this SO question for more background between the two products:
What are the limitations to SQL Server Compact? (Or - how does one choose a database to use on MS platforms?)

I worked recently with it, by the way the things I know about using them is that SQL Express has a server to connect to, and, Compact is a sdf file, so the first thing you will have to change is the connection string to it.
After this change, there are no more heavy changes to be done, I remember, compact has almost all the instructions of the express server available, so, it could not be much problem.
Take a look at Microsoft documentation for more information, or at Wikipedia.
See you.

I would vote against SQL CE:
It has no views, which might be an issue when migrating.
We recently did something similar which you described and had tremendous performance impacts when switching from SQL Server Express to SQL Server Compact Edition.
My recommendations would be:
Use SQLite (which we did for the project I mentioned - it was much more performant than SQL CE in our case) -or-
Use VistaDB (which I did in other projects; not as performant as SQL Server Express, but still sufficient)
Both databases can be XCOPY deployed, just like SQL Server Compact Edition.

SQL CE has the same size limitation as Express, so you should be good.
As far as moving between the two, I found this for moving between express databases and compact 3.5 databases. Then I think you'll only have to change your connection strings (instead of pointing at a host/instance, you point at the converted file). There are different features between the two, though, so you might have to change your schema in the original database for the conversion to go smoothly.

Easiest way to use SQL in a C# application?

I'm making an application in C# (with Express Edition) for which I would like to add some SQL functionality so that the user can query a database. I don't care how or where I store the database. I can store it in a DataTable or a bi-dimensional array or any kind of file. But I want the user to be able to SQL-query it. Apparently this should be quite simple since the .net seems to be full of database libraries and stuff. I was thinking about downloading MySQL and see if I can connect it to my application. I guess if I want to distribute my application then the user would need to download MySQL as well, which is not a big deal but would be great if I can avoid it. Anyway, for now I would like to start working on my program ASAP, so whatever is the easiest way to do what I want, even if it's not distributable, (but if it is then that's even better), will be good. Thanks in advance.

There are embeddable databases. SQL Server Compact Edition and SQLite are common ones. You can execute queries against these just as you can MySQL or SQL Server.
SQLite (.NET)
SQL Server Compact

You can use most popular databases with .NET. SQL Server, Oracle, MySQL, etc. But you're gonna need drivers of each. So, I'd suggest using SQL Server Express Edition to you to get started.
Then you can easily use SqlConnection and SqlCommand classes to connect and execute queries.

You could use a dbml file in your project and link it to your sql database and then run a sql statement using Linq2SQL documented here

I would look at using and embedded database that you can distribute with your application. SQLite is a very good option. You can then use a free ADO.Net library like System.Data.SQLite for data access. It also provides design time support for Visual Studio.

You can use LINQ to Objects or LINQ to Datasets to run LINQ queries with no database whatsoever. You can't use a bi-dimensional array, but you can use a List<> of objects with properties as a LINQ context.
From your question it sounds like your application, like most applications, may need to store the data for later use: that's where a database will come in handy. .NET Datasets have built in support for persistence to an XML file if your data storage requirements are simple enough to use that. .NET also supports persistence for objects, but you may find that using a database is the simplest solution, especially if you require multi-user access and editing.

C# database in a file

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.

Database Choice for a C# 2008 front end

I was wondering what and why you would choose to be able to make a database that can support no more than 100 users with no more than 10 using it at once with a Visual Studio 2008 C# Windows Form front end to access it by. I have to access the database over a network connection, not just on the local machine. I also need to define where the database is found at run-time in the code as opposed to the "Data Source" view in Visual Studio. If my question needs reframing or is not understood, let me know and I will adjust. Part of my problem is I am not sure even how to ask the right question, much less what the answer is.

If it is not for comercial purposes you can try SQL Server 2008 Express. It can integrate nicely with Visual Studio 2008 for development and has support for LINQ, Entity Data Model and ADO.NET Entity Framework to make it easy to create next generation data-enabled applications.
http://www.microsoft.com/express/sql/default.aspx
You can also store your connections strings in the application configuration file and retrieve them programatically for setting up the database connection.
http://www.codeguru.com/columns/DotNet/article.php/c7987/

I would probably go with Sql Server Express, it's free and works well with .NET. Assuming your schema is not changing at runtime you can probably still use the design time data source features in Visual Studio. The connection information is stored in the app.config file which you can update after the app is deployed to point to a different database. You can also develop a class that gets the connection info from somewhere else as well and just use that when you need to open a database connection.

I know using mssql you can pick between different connection strings for all of your db calls, just do something like
Command.Connection = GetMyConnectionWithWhateverLogicINeed();

I'd have a look at Sql Server Workgroup Edition
http://www.microsoft.com/sql/editions/workgroup/
Express edition used to have some limiting features for more than about 5 users and it is not supplied with any management tools which is a bit disheartening.

I'm not sure I totally get what you are asking, Matt, but I can tell you that I developed a series of apps written with VS 2008 and we used a MySQL DB for it. While I'm definitely not a DB guru at this point, I've not had many issues with using MySQL.
Perhaps if you rephrase your question, we can provide better answers.

SQLite for sure.
ADO 2.0 Provider