列挙体メンバーを文字列としてDBに保存

// Alert Level
public enum AlertLevel { Debug, Information, Warning, Error, Fatal }
// Message
public class AlertMessage {
    [Key]
    public int MessaegId { get; set; }
    public AlertLevel Level { get; set; }
    public string Message { get; set; } = null!;
    public DateTime LogDate { get; set; }
}
// DbContext
public class ConvTestCtx : DbContext {
    public DbSet<AlertMessage> Messages { get; set; } = null!;
		・・・
    protected override void OnModelCreating(ModelBuilder modelBuilder) {
        modelBuilder
            .Entity<AlertMessage>()
            .Property(e => e.Level)
            .HasConversion(
                v=>v.ToString(),    // Instance⇒DB
                v=>(AlertLevel)Enum.Parse(typeof(AlertLevel),v) // DB⇒Instance
            );
    }
}

CREATE TABLE [Messages] (
    [MessaegId] int NOT NULL IDENTITY,
    [Level] nvarchar(max) NOT NULL,
    [Message] nvarchar(max) NOT NULL,
    [LogDate] datetime2 NOT NULL,
    CONSTRAINT [PK_Messages] PRIMARY KEY ([MessaegId])
);