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EF Core 3.1: Deleted all Migrations and the Database, how to recreate all tables in a new database?

I deleted all migrations in the migrations folder and also deleted the database in SQL Server.
I know - now - these shouldn't be done, but I need to re-create the database structure to keep the application.
I tried 'add-migration initial' but the it simply generates an empty migration file and an snapshot file. If I try the 'remove-migration' then it complains about some missing migration file.
Is there anyway to 'reset' the snapshot like I just had created the DBContext, so it will create all the tables as in the current DbSet definitions?

I think the following solutions can help you:
First of all, make sure that the database is completely deleted because you said that the database was deleted in SQL. (After you create the first migration, a table called __EFMigrationsHistory is created, where the migration records are stored, if the database is not completely deleted, you must delete this table).
Second, delete the Migrations folder completely.
In the third step, run the following command.
Enable-Migrations -EnableAutomaticMigrations -Force
In the last step, run the following command
Add-Migration Initial
Steps :
Delete the state: Delete the migrations folder in your project
Delete the __MigrationHistory table in your database (may be under
system tables)
Run the following command in the Package Manager Console:
Enable-Migrations -EnableAutomaticMigrations -Force
Use with or without -EnableAutomaticMigrations
And finally, you can run:
Add-Migration Initial
Also this two link can help you :
Reset Entity-Framework Migrations
https://weblog.west-wind.com/posts/2016/jan/13/resetting-entity-framework-migrations-to-a-clean-slate

It seems the problem was in my project!
As #CodingMytra pointed in the comments, there were an active reference to the old database in my project. For some reason it was not rebuilding and not updating, thus not reflecting the changes in the models/dbcontext.
I created a new, empty project, imported all source files, generated a 'Initial' migration and updated the dabase successfully.
Thanks for all replys!

Migration not listed by .net core CLI

I am having trouble updating database from .net core CLI
I have 2 solutions, one that has the connection string in the startup (firstSolution) and another that has the migrations folder and DataContext (secondSolution)
I used this to add migration and I am currently in the secondSolution directory
dotnet ef migrations add migration-name -s ../firstSolution/firstSolution.csproj
and then I tried updating the database like this
dotnet ef database update
But then it made this error
Unable to create an object of type 'DataContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728
so I added the --startup-project (-s) to be able to see the connection string and ran the same command like this:
dotnet ef database update -s ../firstSolution/firstSolution.csproj
it returns this
No migrations were applied. The database is already up to date.
I tried listing the migrations using:
dotnet ef mifrations list
so the same error again
Unable to create an object of type 'DataContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728
so I edited the command to this:
dotnet ef migrations list -s ../firstSolution/firstSolution.csproj
And my new migration wasn't listed in there
So I tried adding the second solution that has the migrations in the startup of the first like this
services.AddDbContext<DataContext>(
options => options.UseSqlServer(connectionString, x => x.MigrationsAssembly("seconsSolution"))
, ServiceLifetime.Transient);
But it also didn't include my migration
Can someone help me how to access the migration in the secondSolution so I can update the database?
I am using VSCode, .net core 3.1 and ef core 3.1.8

So apparently the .csproj didn't include the migration files
once I added them in the secondSolution.csproj it was able to update the database. However I am not sure why it didn't include them in the first place.
<Compile Include="Migrations\migrationName.cs" />
<Compile Include="Migrations\migrationName.Designer.cs" />

Error: The name is used by an existing migration

Recently I run add-migration command, and I have some mistakes, so I run remove-migration to undo it. But when I run add-migration again, it said: The name 'blablabla' is used by an existing migration. How to fix this. I already double check Migration folder, there is no migration that have that name.

Delete bin and obj folder in the src of your project, rebuild and It should allow you to add migrations with the same name. This works for me.
It seems that they are cached in the bin and obj folder and when you try to add a new migration with the same name it checks those folders and throws you the error message.
Tested on .net core 2.2

Try to build your application after removing migration:
dotnet ef migrations add YourMigration
dotnet ef migrations remove
dotnet build
dotnet ef migrations add YourMigration

If you have access to your database, Go to the Database and Remove that Last Migration you add in the migration table. Then it should work again without any problem.

Check the "Data" folder. There are migrations there also. Delete the folder, re-run the build and should work.

Build -> Clean Solution does the job.

Check the \Migrations folder, delete the 'blala' name, both .cs. and Designer.cs. Run the add-migration again , should work.

maybe its exclude from the project. check TFS or file explorer.

EF Core missing Snapshot - Identity Server

I was tasked to update an IdentityServer Application to the newest version.
There are several differences between the ConfigurationDbContext and PersistedGrantDbContext and the current Database.
Usually i would create a migration and then update the Database, but in this project, there are no previous migrations or Database Snapshots.
So if i try to create a migration the whole Context is scripted and not only the changes.
How can i create a migration, that is only a diff between my current DB and the DbContext.

The simplest way should be to create initial migrations based on the context before upgrade, then upgrade dbContext(s) and create migrations for that.
Something like:
dotnet ef migrations add InitialConfigration -c ConfigurationDbContext -o Data/Migrations/IdentityServer/Configuration
dotnet ef migrations add InitialPersistedGrant -c PersistedGrantDbContext -o Data/Migrations/IdentityServer/PersistedGrant
Then delete any code inside the Up() method in your Initial migrations code.
And finally
dotnet ef database update
Here you should have your initial migrations synced with your dbContext, and can upgrade the context and create the first real migration. Actually nothing special for IdSrv.

Where is the mysterious EntityFramework database?

In my main project, I have configured a connection string to my database like this:
<add name="DefaultStoreConnection" "provider....">
In my infrastructure project, I have a database context with a default constructor that passes the connection name to the base class:
public DatabaseContext() : base("DefaultStoreConnection") {}
As soon as my application starts, EF generates a 'store.sdf' (SQLCe database) in the application output folder (\bin).
Now, I wanted to reset all migrations and start with a plain database. I deleted the 'store.sdf' in the \bin directory, deleted all migration files and then called in the Package Manager Console:
Enable-Migrations -Force -ProjectName "MyInfrastructureProject" -StartUpProjectName "MyMainProject".
This worked fine, a new migrations configuration class was generated. Then I ran:
Add-Migration Initial -ProjectName....
And then the following line appears:
A previous migration called 'Initial' was already applied to the target database
Where? Where does this migration has been applied to? Where can I reset this 'migration'?

It should be in a folder containing all the migrations, but it's possible that it's deleted after it has been applied to database. You can see list of applied migrations in __MigrationHistory table of your target database. If you wish to rescaffold the database, empty the __MigrationHistory table.

I run to the same problem as you. After a day of google search without a single useful help, i figured it out myself that this is Visual Studio bug where your solution have more than one Mvc projects. The add-migration will check on the older Mvc project to create migration file for your current project (that is why i call it BUG).
To avoid this, you should only use one Mvc project per solution.

Have a look at the app_data folder of your project.