I am creating a project using Entity Frameworks 4 and self tracking entities. I want to be able to either get the data from a sql server 2008 database or from sql server compact database (with the switch being in the config file). I am using the repository pattern and I will have the self tracking entities sitting in a separate assembly.
Do I need two edmx files? If so, how do I generate only one set of STE's in the separate assembly? Also do I need to generate two context classes as well? I am unsure of the plumbing for all this. Can anyone help?
Darren
I forgot to add that the two databases will be identical and that the compact version is for offline usage.
Just to follow up on this. In the end I had to maintain two separate edmx files, one for sql server and one for compact. The main reason being that compact 3.5 does not support auto identities (as mentioned above by Zeeshan). This in turn led to two context classes. In the context class for sql server compact I had to put code to check for insertions, query the database for the latest id and increment it manually before saving.
Thankfully with the release of compact 4.0 this no longer applies as it supports auto id and you can indeed use just one edmx file.
Darren
You do need the edmx file as long as the schema is exactly the same. just change the connectionstring and everything would work seamlessly. Though i am not sure how u are saying that schema is same when compact edition does not support identity concept and full blown sql server does. So if you are using features specific to sql server that's not available in compact, then you would get runtime errors.
Related
This is a long question, but I would be very very thankful if I can get some good advice on this. In short, I’m looking for a good approach for version upgrade of MS SQL database schema that also demands data being moved from deleted tables into new tables.
I think Stack Overflow is the most appropriate place for this question (not dba.stackexchange.com) because at its core, this is an issue for .NET developers using Entity Framework, and the database parts of this consists mostly of auto-generated sql scripts.
Background
A .NET application and SQL database is running in Azure (The application in worker roles and the database in Azure SQL). Until now, version upgrades have worked fine, because all database schema changes have been simple (like adding a new column). However, from now on I also need to deal with moving data from one table to another during upgrades. (I’m able to fix this temporarily by creating a new database, generate a script with data from the old database and manually edit the script to make it fit the new schema, but I hope there is a better approach).
I use Entity Framework and I use Model First. Entities and associations are defined in Visual Studio Data Model Designer, and this approach is very appropriate for my application.
I use a dacpac to upgrade the Azure SQL database, and this approach has worked well until now (but now I will get data loss, so now I must find a way to move data to new tables).
I hope I can continue to use entity framework and defining entities/associations in the designer, but it’s fine to switch away from dacpac upgrade to another technology if needed.
Upgrade approach until now
I add new entities (tables), associations (relations) and properties (columns) in the designer.
I right-click, pick “Generate Database from Model…” and this results in a .sql script that drops old database objects and creates the new database objects.
I create an empty database and run the script to create the tables/keys etc.
In SQL Server Management Studio, I right-click the database and pick “Tasks -> Extract Data-tier Application…”. When the wizard completes I get the dacpac I need (Actually I can now delete the database, since I only created it to be able to get the dacpac file, since I don’t think I can generate it in Visual Studio Data Model Designer).
I right-click the Azure SQL database and pick “Tasks -> Upgrade Data-tier Application…” and follow the wizard.
Until now I have never had data loss, so this has worked fine!
Current situation
This is a simplified example to illustrate the issue, but I will get into almost identical situations quite often from now on it seems. Look at the old and the new version of the schema in the figure below. Assume there is already data in the database. I need the data in ImageFile to end up in ImageFileOriginal or ImageFileProcessed depending on the IsOriginal boolean/bit value. Using “Upgrade Data-tier Application” I will get alerted of data loss. What approach would you recommend to deal with this? As I said earlier, it’s fine to switch away from dacpac upgrade to another technology if needed.
I have read about Visual Studio Database Projects, Fluent Migrator, Red Gate and Entity Designer Database Generation Power Pack (It doesn't support Visual Studio 2012), but I didn’t find a good way for this. I admit I haven’t spent a whole day digging into each technology, but I certainly spent some time to try finding a good approach.
The best way to migrate database schema (create / delete tables / columns) and also data, is using the SSDT - Sql Server Data Tools, available for Visual Studio 2010 and Visual Studio 2012.
Here are some very useful links:
http://msdn.microsoft.com/data/tools
http://blogs.msdn.com/b/ssdt
http://msdn.microsoft.com/en-us/data/hh297027
In the Configuration class set the constructor as below:
public Configuration()
{
AutomaticMigrationsEnabled = true;
AutomaticMigrationDataLossAllowed = false;
}
Set the AutomaticMigrationEnabled property to true
means we are using automatic code first migration and another property AutomaticMigrationDataLossAllowed is set to false, means that during the migration no existing data is lost from that migration of the table of the database.
The entire Configuration class is as follows.
I'm forced to use a legacy SQL Server 2000 database for an EF-based app I am writing. The tables already exist, so I need to generate the Entities layer. I can do this in VS2010 using MySQL and recent versions of SQL Server, but not 2000.
To get around this, I followed some tutorials that explain how to generate csl, msdl and ssdl files using edmgen.exe.
That works fine. I now have those files in e.g. c:\temp.
Please can someone tell me what to do with these files? I want to Entity Framework-ify a simple console application that I have written. Can I somehow create an 'ADO.NET Entity Data Model' from these files so I end up with what I would have if I had used VS2010 all along?
Thanks
I got it working, here is what I did
1) Use edmgen.exe to generate the files mentioned in my question
"C:\windows\Microsoft.NET\Framework\v4.0.30319\edmgen.exe" /mode:fullgeneration /c:"Data Source=<your_server_here>; Initial Catalog=<your_catalog_here>; UID=<username>;PWD=<password>" /project:<vs2010_project_name> /entitycontainer:<project_name>Entities /namespace:<project_name>Model /language:CSharpEntityFramework
2) Follow these instructions "How To: use your existing CSDL/MSL/SSDL files in the Entity Designer CTP2" - its actually for VS2008 but it worked for me too.
http://blogs.msdn.com/b/dsimmons/archive/2007/12/07/how-to-use-your-existing-csdl-msl-ssdl-files-in-the-entity-designer-ctp2.aspx
3) I had a further problem in that my legacy db had no primary keys so I followed these instructions which also worked
http://pratapreddypilaka.blogspot.in/2012/04/entity-framework-adding-datatable-with.html
These files are referenced in EF's connection string and EF use them at runtime to build a mapping but it can still not work because SQL Server 2000 is not supported by EF (at least EF 4.0 and newer). EF can generate SQL not supported by SQL Server 2000 and you will get exceptions at runtime.
Setup
I have a SQL Server 2008 database that is accessed using the Entity Framework on the server.
Each client has a SQL Server Compact Edition 3.5 database for storing data when offline.
I use self tracking entities that are generated from the server defined Entity Framework.
Question
At the moment i have two EDMX defined, one for the server and another for the client, even though they are identical except for the storage provider. I use the self tracking entities from the server and they work fine with the client database. Is there a way to have just a single EDMX? At the moment there is a risk I will make a change to one EDMX and forget to make it to the other. Or am I using the wrong approach?
Note
I do not want to use the sync framework because of complex business logic that needs applying at the server side.
Unfortunately there is no direct way to use single EDMX with multiple storage providers. You must always have separate SSDL part for each provider. The common workaround is to export SSDL, MSL and CSDL as separate files (default setting adds them as resources to assembly) and use some script or pre-build action to create copy of SSDL file with all necessary changes for second provider (there can be also different data types between SQL Server and SQL Server CE). You will than use correct SSDL file per application by specifying it in connection string.
Another "better" solution is not using EDMX and use code first where this problem mostly doesn't exist - but that is architecture change.
I have a MVC3 website I have been playing with, and the database is quite well populated. I need to change the underlying models, but of course, the standard approach would drop all data. Having the CREATE SQL (so I can ensure all fields/relationships are in line with the models), and the calculated hash (so EF thinks the models match the database) would allow me to manually make changes to the database.
Is there a way to interrogate a DataContext (or some other object) to:
1. Get the SQL it would use to generate the dataschema; and
2. Get the ERM Metadata hash
I have considered some other migration options, but just want to explore this avenue.
Edit: This is EF4.1, and is running against SQL 2008 R2 if that is of any relevance.
Thanks
Andrew
You can do it with EF Migrations. You'd need to upgrade your project to EF 4.3. You'd use the "Update-Database -Script" ps command.
Here is a link to the ASP.Net team blog on it: http://blogs.msdn.com/b/adonet/archive/2012/02/09/ef-4-3-code-based-migrations-walkthrough.aspx
Pluralsight also has a course on it. They also have a free trial. http://www.pluralsight-training.net/microsoft/Courses/TableOfContents?courseName=efmigrations
As the title says, how do I view the SQL generated by Entity Framework from within my code? I'm running into an error where the EF is crashing because a field is generated by the database (a DateTime field), and I thought I set it to know that the store is generating it via StoreGeneratedPattern, but it's still crashing, so I would like to see what exactly it's trying to push up to the database.
P.S. I've only been using EF for about an hour now... Switching from L2S.
Since you don't have Sql Profiler, your best choice would be LINQPad. You can use your existing assembly.
Click Add connection -> Use a typed data context from your own assembly -> Entity framework and select your dll.
You can write queries directly against your model (or copy-paste from your code). Select the SQL 'tab' under the query window to view the generated SQL code.
You can use the Entity Framework Profiler (EFProf). It's not free, but there's a 30-day trial available. It does a lot more neat stuff besides showing you the SQL statements.
Generally, you should always use SQL Profiler to see the SQL statements that being submitted by EF into your database.
Also, I think you misunderstood about what StoreGeneratedPattern is. If you look at its possible values inside the model, you'll see that it has identity meaning that the value will be generated (by the database) when the row is inserted and will not otherwise change. The other options are Computed, which specifies that the value will be generated on inserts and updates, and None, which is the default.
So EF will not generate that DateTime field on the fly for you, you need to manually create it and then update your model from database so that EF will generate appropriate metadata to work with it at runtime.
The free AnjLab Sql Profiler will work if real SQL Profiler is not available because you're using SQL Server Express: http://anjlab.com/en/projects/opensource/sqlprofiler. It's not quite as nice as the real thing but it gets the job done well enough.
One solution would be to capture the network traffic and have a look at the data on that level. Microsoft Network Monitor does a good job of this.
Of course, that only works if you're using a separate DB server, and the connection is not encrypted.