Develop Reference

SQL table getting deleted by itself in local db, using LINQ to SQL [duplicate]

I'm making a WinForms app in C#. When I go to create my database object, I'm presented with two options:
Local Database
Service-based Database
All I want is a simple local database to use for my project.
However, if I select "Local Database (Compact Edition)" then after I create my tables and drag them over to a LINQ-To-SQL Class creator it says:
The selected object(s) use an unsupported data provider.
So, I don't know why creating a local database would be considered an unsupported provider when dragging to tables to the Object Relational designer.
So, I try the second type, "Service-based Database". I lay out my tables how I want for my basic application and make my tables. The LINQ-To-SQL Designer works fine when I drag these tables and I proceed to write my code in my app to insert and upate the database entries.
However, with this second "Service-based Database" my inserts and updates work as long as the application is running. However, once I close it it reverts back to what it was before. If I manually add in data via the Server Explorer it persists but any inserts I do don't save.
Why can't I create and use a Local Database with LINQ?
If that isn't an option, then why isn't the "Service-Based Database" (whatever that is), persisting beyond the application closing?
Thanks for your time!
Edit: Apparently the LINQ-To-SQL Object Designer doesn't work on Compact Edition Local Databases. It can still be done, but you have to use SqlMetal apparently to generate the dmbl file.

When you compile, the old database gets erased and a new one is copied to the bin folder. Therefore try link (using linq) to the database in the bin folder. Try change your connectionString.

C# Edmx - update a database

I have a question. I have a project that uses an edmx and all hooks up fine to the sql server.
I have installed it in several servers.
What I want to know is, having made changes in development so m database and my edmx are change,s say a new table and a modified one.
How do I make it so these updates are aplied automatically when I publish an app update?
I remember once a long time ago doing code first database work and making some kind of file or procedure that would automatically apply these changes when the app ran.
Can any one fill me in again.

1.- AFAIK, when you're using model first or database first, you can't use Migrations, you generate a DDL script that when executed, creates the database or drops and recreates tables losing any data you had.
See This link read point number 5.
"The script that is generated will drop all existing tables and then recreate the schema from scratch. This may work for local development but is not a viable for pushing changes to a database that has already been deployed. If you need to publish changes to a database that has already been deployed, you will need to edit the script or use a schema compare tool to calculate a migration script."
What I do here, is make the changes to the database and update the model (Right click edmx designer, click "update model from database")
2.- You can configure updates on a ClickOnce installer, any changes made to the edmx will be published on your app.

How to import existing mdf file into a lightswitch project?

I would like to copy table definitions from an existing database file into a new lightswitch project, does anyone know how to do that, it seems like you can only create a new database from scratch or attach an external database, but when i try to attach an external mdf file from another VS project I get an error which states: CREATE DATABASE Permission denied in database 'master'.
Any ideas about how to copy the table definitions from an existing database file into a lightswitch project?

If you have the external database attached on an instance of SqlServer, you shouldn't have no problem attaching to it from LightSwitch. From that point on, you can rename tables and columns, change datatypes etc, as well as adding more tables and structures to that DB.
Note that the DB is supposed to be served from a SqlServer instance, not a file on your file system.

As far as I know it can't be done. Lightswitch holds a representation of the database tables separate from the actual database definition. You can probably go the other way however because when the ApplicationDatabase.mdf file does not exist you can start Lightswitch (you will notice the table definitions are still in there) and then build the app which will recreate your ApplicationDatabase.mdf. It is empty of course but If you could find out where lightswitch stores those table definitions (an *.xaml file somewhere?) you might be able to get those copied into your project and then generate the ApplicationDatabase.mdf from there?

Databases in winforms c#

I can't understand how to manage database with Entity Framework.
I'll try to describe my problem step-by-step
create winforms application
add database (.mdf) to solution
when appears window "choosing database model", select dataset
then finish, as database is empty
go to server explorer, choose created database, create some tables
add to solution EDM ADO.NET
The problem is that new data doesn't appear in my database in server explorer. This means that while my Winforms app is working, I can modify my database (change existing values, add new, ..). but if I close my app, there is no update in my database in server explorer. I DON'T forget to use function SaveChanges()
P.S. while my app is working, values are updating. Think, that means that data updates in dataset, but not in database. if i am right, give a clue how to update database from dataset.
pps. visual studio 2010 ultimate. sorry for english
dbentity db=new dbentity();
db.items.addobject(new item() {value=something});
db.savechanges();

Don't add the database to your solution. You can use the Server Explorer to add a connection to your database via your existing SQL Server, or you can select your database in the wizard that appears when adding a new EDMX file to your solution.
Did you try either of these? Where did you get stuck?

LINQ-to-SQL not submitting changes to local database

I have a local, SQL Server Compact database in an application I am creating. I generated a .dbml file I can use for LINQ-to-SQL purposes using the SqlMetal.exe tool, which worked fine - I now have the table objects for use in my application.
I have a strange issue though. Even after calling SubmitChanges() on my DataContext, the data never commits. But strangely, after adding the rows, these rows do appear in the table object on the datacontext, but not in the table. What shocked me is even after stopping and starting my application, these rows still existed in the DataContext - but after a few minutes they seem to disappear.
Have I configured this correctly? Are there any more steps I need to do after using SqlMetal to allow the LINQ to commit changes?

I am assuming that you linked to the dbml file using the default properties. This means that, each time you start a debug session, the file will be copied into your output directory and changes made to it will only be seen for that session (i.e., "Copy -> Always").
If you want the changes to persist then right click the file -> properties -> Copy Never. By default the IDE assumes that you don't want to modify the original database, only a copy for debugging purposes.