Suppose I have an existing database set up using Entity Framework. Is there a mechanism through which I can safely add or remove entities (or their properties) such that the database is altered automatically?
I know there's an option to "Update Model From Database". Is there an equivalent "Update Database From Model" ? Is there a way to configure Visual Studio to do this automatically?
Entity Framework 4.3 has Code First Migration support.
EF helps you with checking the differences between your code and database and then generates code for you that handles this changes. You can use the NuGet package manager console to enable migrations, add a new migration and run them against your database (or create a sql script).
This blog explains how the Migrations work and this blog shows how you can use it with an existing database
Altering the database schema isn't a straightforward operation (has a column been renamed, or is it new column? Can the old type be converted to the new type?) that you can easily infer from the model.
EF doesn't alter the tables for you - it can Drop-Create the DB for you when you change it. However, if you change the existing database by hand to suit the model, EF doesn't seem to mind. It looks like what they check for is Hash(Model) = Hash(Tables).
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Is possible update database table from edmx model, for example if I create a new field in edmx diagram to a table, I want update corresponding mapped table in database adding this new field ... in visual studio menu I find the voice "update model from database" and "create database from model" , but I not find "update database from model"...
In the EF EDMX "Model-First" workflow you always generate a full database DDL script, and for incremental changes use a schema-compare tool like SSDT to create the change script.
See eg https://learn.microsoft.com/en-us/ef/ef6/modeling/designer/workflows/model-first#5-dealing-with-model-changes
It's not a very popular or useful workflow, and the tooling for incremental updates was just never built. The vast majority of EDMX users do a database-first workflow with no customization of the EDMX.
But you should really stop using EDMX. The graphical designer seems simpler to begin with, but using code-based mapping is simpler in the long run.
I don't believe Edmx (database fist) works that way, at least, out of the box. You need to use code first, and enable migrations.
Edmx is nothing more than mapping to your data, that doesn't tie into migrations.
I believe there is a way to auto-generate your code first as well using visual studio...just like the Edmx.
My team has inherited a database application that contains hundreds of tables. The application uses Entity Framework and takes a database first approach for development. Our current process is to pull a table or two at a time into the edmx using the Update Model From Database... tool.
We are considering making a new API with .Net Core, but as far as I can tell from the research I have done, there is no equivalent process in the Entity Framework Core tools. The closest thing I can find is to reverse engineer the entire database with Scaffold-DbContext, and then use migrations for all future database changes. We can't scaffold the entire database, because some of the tables have errors, and fixing all those errors is not a viable option for us right now.
I have found that I can supply a list of tables that I want scaffolded with the initial Scaffold-DbContext call, but I'm not sure if migrations can be used in a similar way to the Update Model From Database... tool. Can I use migrations to add tables that already exist in our database? If not, what other options should I be looking at?
I'm pretty new to Entity Framework: I started from a database-first model to maintain an application created using a strange mixture of EF and plain old SQL.
I created my own fresh DB-first model and I'm fine with it. Today my boss asked me to add a new entity. Lack of foreign keys simplifies the scenario.
I have created my new entity in the diagram (it's made of three instances of a Complex Entity I just created) but now I have to make an incremental DB script to create the new table. I'm supposed to do that both for MySQL and SQL Server but let's start with the second.
So now I see that I have a compilation problem "No mapping for entity Entity" and if I use "Update model from database" command I see no option for pushing changes to DB, but that sounds correct given the word "from".
OK, I have tried to click "Table Mapping" from the right-click menu and I found the option to map the entity to the table. I was going to type the new table name in the "Add table or view" field and... WAIT! I can only select existing tables
I understand it's just for a single table so I can simply "Generate database from model" in order to get the full SQL script, find the table I want, run that to DB and "Update model from DB" so EF will see the table, BUT
I would like to understand how to create incremental scripts with Entity Framework. That is my question.
You indicate you have a database-first design but appear to be working from a code-first mindset.
In database-first design the entity model is subordinate the underlying datastore. Changes to the model (or at least changes to the model which also require changes to the underlying datastore) occur FIRST on the database.
So how do you create a new table for the entity? You create the new table in your database (CREATE TABLE ...). Then using the "Update Model From Database" wizard you select the new table from the "Add" tab. EF will create the corresponding EF class automatically. If you already manually created the entity you should delete it otherwise you could end up with some weird entity naming (i.e. Customer1).
Database first does not have the capability to support table creation at the entity layer. Changes to the database are always one way, from the database to the entity model, hence the term "database first".
On the other hand if you are more comfortable creating entities directly and want to build a database from a set of entities you should be looking to create a "Code-First" design. Despite the name "code first" it is possible to get an initial set of entity classes from an existing database. The term "code first" refers to the origination of changes to the db/model structure.
We have a fairly elaborate data model built from an existing database, then enhanced using partial classes to support additional methods & properties, inheritance, etc. We have not yet bitten the bullet to update this from ObjectContext to DbContext.
I am using VS2012, .net 4.5, EF 6.0.2, and have installed the EF 6.0.2 Tools for VS2012.
Following the recommended mechanism to update a project to EF6 (http://msdn.microsoft.com/en-us/data/dn469466) has been successful, including the addition of the EF 6 Entity Object generator as the code generation item.
Subsequent to making this change, I would like to update the model from the database to incorporate some recent schema changes into the model. Running through the "update model from database" dialog, what appears to be happening is that an entirely new dbcontext-based model & template is added to the project, in addition to the object context-based model that already exists in the project, and none of the changes are incorporated into the entity-object template.
Of course, this means there are hundreds of duplicate names defined in the project once the operation completes. The edmx properties do not appear to have an option that would control this behavior.
Certainly, making the transition to dbcontext is the right avenue ultimately, but would like to avoid taking that on imminently.
My experience is open edmx file in visual studio by double-click and then select all tables perform a full delete(press del). Then click save button on top of menu bar, it should delete all models automatically.
After it's done, then you can update model from database again.
Hope this helps.
I am using NHibernate and Fluent NHibernate for the first time. I had to physically create the database and write SQL scripts for the first 2 tables. Now, i am wondering if this technology (NHibernate), like Entity Framework (Code First) when you have enabled migrations has a similar too to create and update tables?
This is what i mean by Ef Code First Automatic Migrations
nHibernate does support schema changes using SchemaUpdate
See: Is NHibernate SchemaUpdate safe in production code?
You can also generate a create script to execute against your database using nHibernate SchemaExport.
SchemaUpdate is not recommended for production use because of the security privileges that have to be granted in order for this to work. Personally I think you should look at a code based migrations tool which are designed to handle initial database creates plus full revision control, I use Migrator.NET - Database migration in C#