Develop Reference

Updating a SQLite Database to reflect a change to the model with Entity Framework Core and .NET 6

I've created a dbcontext that looks like this:
public class DatabaseContext : DbContext
{
public DbSet<Author> Authors { get; set; }
public DbSet<Book> Books { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlite(#"Data Source=E:\Portfolio\FullStack\HomeLibraryManager\Database\Library.db;");
}
}
And I Initialize it like this:
using (var context = new DatabaseContext())
{
context.Database.EnsureCreated();
var books = context.Books.ToList();
}
I would like to add a variable to my Book class but how do I get the database table to have that new variable added as a column.
I had hoped that EnsureCreated() would make sure the table columns were updated if needed but it seems not.
Any help would be great,
thanks
Edit Solution:
I used context.Database.Migrate(); instead of EnsureCreated and ran dotnet-ef migrations add [MigrationNameHere] first

Run the Add-Migration AddUrl command in Package Manager Console. The Add-Migration command checks for changes since your last migration and scaffolds a new migration with any changes that are found. We can give migrations a name; in this case we are calling the migration ‘AddUrl’. The scaffolded code is saying that we need to add a Url column, that can hold string data, to the dbo.Blogs table. If needed, we could edit the scaffolded code but that’s not required in this case.
Run the Update-Database command in Package Manager Console. This command will apply any pending migrations to the database. Our InitialCreate migration has already been applied so migrations will just apply our new AddUrl migration. Tip: You can use the –Verbose switch when calling Update-Database to see the SQL that is being executed against the database.
Dealing with Model Changes

Entity Framework Database First - How to prevent running the initial migration?

I was able to scaffold an existing database using EF Core recently. We want to completely migrate to EF Core, but we've hit some snags and I need your help.
We began by running the scaffold command and ended up with this file structure
C:\>ls .\EFCore
Context
Models
EFCore.csproj
Then after creatinng the Context and the Models, I ran the inital migration command.
dotnet ef migrations add CreateDb
After running that command our directories look like this
C:\>ls .\EFCore
Context
Models
Migrations
EFCore.csproj
C:\>ls .\EFCore\Migrations
20210616210256_CreateDb.cs
20210616210256_CreateDb.Designer.cs
DbContextModelSnapshot.cs
My Problem
The database is already created in all environments, so we don't want entity to execute the inital database migration. Should I delete 20210616210256_CreateDb.cs and 20210616210256_CreateDb.Designer.cs to achieve this?
The other route I can think of is create the __EFMigrationsHistory table and insert a row into it. This would fake that we've already ran the inital db create.
Help please, I would like to do this the cleanest way possible.

Remove/Comment the code inside your Up() and Down() methods of migration file and call update database. You don't want the code which creates table i.e.
CreateTable(
"dbo.YourTable",
c => new
{ //Properties set here })
Your migration class could look like this -
public partial class Initial : DbMigration
{
public override void Up()
{
}
public override void Down()
{
}
}

Code First Automatic Migration

The current project I am working on, I am telling Entity Framework to do nothing by setting SetInitializer with params null:
public EfDbContext()
{
Database.SetInitializer<EfDbContext>(null); //new NullDatabaseInitializer<EfDbContext>());
}
I have a script that creates a few table. When I running the script, it is creating the dbo.__MigrationHistory in the DB.
How can I disable migration, I thought the above code would disable that.
Am I missing something? I also don't have migration enabled and any configuration files for migration.
I am using EF 6.1.3.

In your migrations folder there is a file called Configuration, in the constructor try something like this:
public Configuration()
{
AutomaticMigrationsEnabled = false;
}
The ugly but easy way to disable the migrations at all regardless the configuration is deleting the table dbo.__MigrationHistory.

I fixed the issue by adding the following code into the Application_Start() in Global.asax:
Database.SetInitializer(new NullDatabaseInitializer<DbContext>());

RenameColumn during db migration in Entity Framework

I noticed strange thing with db migration that I couldn't fix.
Please help.
I have a class
public class Subscription : BaseEntity
{
...
[Index("IX_Subscription_Status", IsUnique = false)]
public int? Status { get; set; }
...
}
I renamed property Status to BeforeStatus and ran Add-Migration command in Visual Studio.
It generates:
DropIndex(...IX_Subscription_Status...);
DropColumn(... Status ...);
AddColumn(... BeforeStatus ...);
CreateIndex(...IX_Subscription_BeforeStatus...);
I didn't want to drop column, so I changed migration script to
DropIndex(...IX_Subscription_Status...);
RenameColumn(...,Status,BeforeStatus)
CreateIndex(...IX_Subscription_BeforeStatus...);
and ran Update-Database migration. It passed without errors and changed the database.
I added a new property AfterStatus to the class
[Index("IX_Subscription_AfterStatus", IsUnique = false)]
public int? AfterStatus { get; set; }
and ran Add-Migration command. It generates:
AddColumn(... AfterStatus ...);
CreateIndex(...IX_Subscription_AfterStatus...);
I ran Update-Database migration and it passed without errors and changed the database.
So from my point of view, everything is correct and db corresponds c# code. I checked __MigrationHistory table, it contains all latest migrations.
BUT, when I run code, it fails with a DbContext error:
The model backing the 'MyContext' context has changed since the database was created. Consider using Code First Migrations to update the database
If I run Add-Migration command again, it generates:
DropIndex(...IX_Subscription_Status...);
DropColumn(... Status ...);
AddColumn(... BeforeStatus...);
CreateIndex(...IX_Subscription_BeforeStatus...);
AddColumn(... AfterStatus...);
CreateIndex(...IX_Subscription_AfterStatus...);
Why? Why does it generate migration script? Is this error related to RenameColumn operation? Maybe it is because of manually changes of migration script?
Please, does anybody know how to make Entity Framework understand that I have already updated the database?

Entity code first migrations and deleting databases

We're using EF Code First and migrations for a project. We're commiting our migrations to source, and everything is great. However, if someone delete's their database, or we get a new person on the project, the database will throw errors because it's trying to run the migrations. Is there a way to make it so that if the database doesn't exist, it ignores migrations? I can't seem to find anything about this.

I would look at how you are using DbMigrationsConfiguration from the Entity framework. You might need something like this in your global asx file:
Database.SetInitializer(new MigrateDatabaseToLatestVersion<YourContext, YourConfiguration>());
Then in your configuration file for migrations you may need something like this:
internal sealed class YourConfiguration : DbMigrationsConfiguration<YourContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = true;
}...
Without more info and code examples, I can only point you in the right direction.