Entity Framework connection string for update-database

Question

I can't figure out how to handle connection strings in EF and NetCore

I have a solution with EntityFrameworkCore 3.1.7 and two projects:

WebApp.csproj
ShraedLibrary.csproj
   - appsettings.json

All data connection stuffs are in ShraedLibrary, where I have this constructors:

public DatabaseContext (DbContextOptions<DatabaseContext> options, ILoggerProvider loggerProvider)

This works fine, but I cannot Update-Database using the connection string from appsettings.json because there is no parameterless constructor.

When I hardcode the connection string inside a parameterless constructor then it works

What is the right way of doing this?

[EDIT]

Don't use -Project in Update-Database solved the problem.

Ventsislav Petrov · Accepted Answer · 2020-08-21 11:40:11Z

1

Presumably, you need to create IDesignTimeDbContextFactory<TContext>.

EntityFramework Core migrations works by running your code, if that isn't possible (as it is your case with the shared library), then you need to provide more information about how your DbContext could be created. For that purpose you can use this IDesignTimeDbContextFactory<TContext> factory.

answered Aug 21, 2020 at 11:40

Ventsislav Petrov

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5 Comments

Carlos Garcia Over a year ago

Why can't my code be run? what is the difference for it to be in a library? - I will check the IDesignTimeDbContextFactory<TContext> now. Thanks! :)

Ventsislav Petrov Over a year ago

Your library doesn't have access to the startup of you app, where you have configured the DbContext (in the ConfigureServices(...) method). So, it doesn't know from where to get the connection string.

Carlos Garcia Over a year ago

why it cannot? Should't it work if I do Update-Database -StartupProject WebApp -Project SharedLibrary ?

Ventsislav Petrov Over a year ago

How have you configured EF in the services? Can you try using CLI, not PMC. Also, what error it gives you?

Carlos Garcia Over a year ago

I figured out, you don't need to do -Project but only -StartupProject. Your answer pointed me in the right direction, Thanks!

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