ForumConfiguration.cs

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
using Tsi1.DataLayer.Entities;

namespace Tsi1.DataLayer.EntityConfiguration
{
    public class ForumConfiguration : IEntityTypeConfiguration<Forum>
    {
        public void Configure(EntityTypeBuilder<Forum> builder)
        {
            builder.HasKey(x => x.Id);

            builder.Property(x => x.Name)
                .IsRequired()
                .HasColumnType("character varying(50)");

            builder.HasOne(x => x.SectionItem)
                .WithOne(x => x.Forum)
                .HasForeignKey<Forum>(x => x.SectionItemId);
        }
    }
}