How to seed an enum in Entity Framework Core 2.1

Question

How to seed an enum in Entity Framework Core 2.1

.net-core asp.net asp.net-core entity-framework entity-framework-core

Question

I am new to EF Core, and am trying to seed an enum.

According to Data Seeding, this feature is new to EF Core 2.1.

I reviewed several solutions including this SO solution by Blake Mumford, but this doesn't work for me since an enum is not a reference type.

My goal (with the help from migrations) is to have the Category enum to be populated in a new SQL table called Category, and have my Payment table contain a column that references the Category table as a foreign key.

Any help would be greatly appreciated. Thanks.

public partial class Payment
{
    public int PaymentId { get; set; }
    public DateTime PostedDate { get; set; }
    public string Vendor { get; set; }
    public decimal Amount { get; set; }

    public virtual Category Category { get; set; }
}

public enum Category
{
    Restaurants,
    Groceries,
    [Display(Name = "Home Goods")]
    HomeGoods,
    Entertainment
}

public partial class MyDbContext : DbContext
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // Error: The type Category must be a reference type in order to use it as parameter TEntity in the 
        // genric type or method ModelBuilder.Entity<TEntity>()

        modelBuilder.Entity<Category>().HasData(Category.Restaurants, 
                                                Category.Groceries, 
                                                Category.HomeGoods, 
                                                Category.Entertainment);
    }
}

Pavel

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Demodave · Accepted Answer · 3/10/2020 4:42:26 PM

This is what I did hopefully it will work with your environment.

Environment

Project Framework

.NetCore 3.0

Nugets:

EFCore 3.1.2
EFCore.Design 3.1.2
EFCore.Tools 3.1.2
EFCore.Relational 3.1.2
EFCore.SqlServer 3.1.2

Implementation

Add OnModelCreating

public partial class MyDbContext : DbContext
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // Error: The type Category must be a reference type in order to use it as parameter TEntity in the 
        // genric type or method ModelBuilder.Entity<TEntity>()

        modelBuilder.Entity<UserRole>().HasData(EnumFunctions.GetModelsFromEnum<UserRole, UserRoleEnum>());
    }
}

Create a Generic Enum Function

public static class EnumFunctions
{
    public static IEnumerable<TModel> GetModelsFromEnum<TModel, TEnum>() where TModel : IEnumModel<TModel, TEnum>, new()
    {
        var enums = new List<TModel>();
        foreach (var enumVar in (TEnum[])Enum.GetValues(typeof(TEnum)))
        {
            enums.Add(new TModel
            {
                Id = enumVar,
                Name = enumVar.ToString()
            });
        }

        return enums;
    }
}

Create an Interface

public interface IEnumModel<TModel, TModelIdType>
{
    TModelIdType Id { get; set; }
    string Name { get; set; }
}

Apply the interface to the model

[Table("UserRoles")]
public class UserRole : IEnumModel<UserRole, UserRoleEnum>
{
    [Key]
    public UserRoleEnum Id { get; set; }
    public string Name { get; set; }       
}

Add your migration
```
PM> add-migration SeedUserRoleTable
```

You should see the migration added

Update the database with the seeded info
```
PM> update-database
```

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