ef code-first

AzureDBContext.cs

using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Text;

namespace Sample
{
    public sealed class AzureDBContext : DbContext
    {
        public AzureDBContext(DbContextOptions<AzureDBContext> options) : base(options)
        {

        }

        public DbSet<SehirEntity> Sehir { get; set; }
        public DbSet<IlceEntity> Ilce { get; set; }
    }
}

Ilce.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Threading.Tasks;

namespace Sample
{
    public class IlceEntity
    {
        [Key]
        public int id { get; set; }

        public int sehirId { get; set; }

        [ForeignKey("sehirId")]
        public SehirEntity sehir { get; set; }

        public string isim { get; set; }


    }
}

SehirEntity.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Threading.Tasks;

namespace Sample
{
    public class SehirEntity
    {
        [Key]
        public int id { get; set; }

        [Required]
        public string isim { get; set; }

        public virtual ICollection<IlceEntity> ilceler { get; set; }
    }
}