Generating Entity-Framework classes for .NET Core projects in a Database First scenario

Microsoft provides two command line tools in situations when there is a need to generate Entity Framework classes for a .NET Core project. Within the Package Manager console of Visual Studio you can use Scaffold-DbContext and if you are using the .NET Core CLI then the command dotnet ef is available. Details on the capabilities (migration, scaffold, update, drop, and more) as well as instructions on what needs to be installed can be found on EF Core tools reference – .NET Core CLI and Entity Framework Core tools reference – Package Manager Console in Visual Studio.

When using dotnet ef command in the .NET Core CLI you will add the scaffold argument which will allow you to generate classes for an entire database, specific tables, or schemas within a database. If you are using it against a specific set of tables then you will provide each table with the –table flag preceding the table name.

In this example the command will generate EF classes in order to interact with two common Identity tables, AspNetRoleClaims and AspNetRoles, within the dbo schema.

dotnet ef dbcontext scaffold "Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=IdentityServer;" Microsoft.EntityFrameworkCore.SqlServer --table dbo.AspNetRoleClaims -table dbo.AspNetRoles

Having the tool generate classes for a schema is just as simple. Instead of using the –table use –schema and provide the schema name.

If there comes a need to regenerate tables or add more then you will need to use the –force flag. This will allow the process to overwrite any files that already exist in the project. Make sure you include all tables or schemas that you want generated. Even if a table hasn’t changed since the earlier schema change you will still need to list it when regenerating the classes.

If you prefer to use the Package Manager console then the same command from above could be executed using only small changes. Instead of a flag for each table you will combine all tables in a space separated list within enclosing quotes.

Scaffold-DbContext -Provider Microsoft.EntityFrameworkCore.SqlServer -Connection "Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=IdentityServer;" -Tables "dbo.AspNetRoleClaims dbo.AspNetRoles"

This post went over only a small portion of the capabilities that these tools provide. If you are designing a system to be a Code First approach then you’ll become very familiar with these tools as you generate initialization and migration scripts. If you are unfamiliar with with EF migrations then take a look at Managing Database Schemas to guide you through each step.