Database-First approach in Entity Framework Core

CREATE TABLE [dbo].[Department](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Name] [varchar](50) NOT NULL,
 CONSTRAINT [PK_Department] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

CREATE TABLE [dbo].[Employee](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [DepartmentId] [int] NOT NULL,
    [Name] [varchar](100) NOT NULL,
    [Designation] [varchar](25) NOT NULL,
 CONSTRAINT [PK_Employee] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
 
GO
 
SET ANSI_PADDING OFF
GO
 
ALTER TABLE [dbo].[Employee]  WITH CHECK ADD  CONSTRAINT [FK_Employee_Department] FOREIGN KEY([DepartmentId])
REFERENCES [dbo].[Department] ([Id])
GO
 
ALTER TABLE [dbo].[Employee] CHECK CONSTRAINT [FK_Employee_Department]
GO

using System;
using System.Collections.Generic;

namespace DatabaseFirst.Models
{
    public partial class Employee
    {
        public int Id { get; set; }
        public int DepartmentId { get; set; }
        public string Name { get; set; }
        public string Designation { get; set; }

        public virtual Department Department { get; set; }
    }
}

using System;
using System.Collections.Generic;

namespace DatabaseFirst.Models
{
    public partial class Department
    {
        public Department()
        {
            Employee = new HashSet<Employee>();
        }

        public int Id { get; set; }
        public string Name { get; set; }

        public virtual ICollection<Employee> Employee { get; set; }
    }
}

using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata;

namespace DatabaseFirst.Models
{
    public partial class CompanyContext : DbContext
    {
        public CompanyContext()
        {
        }

        public CompanyContext(DbContextOptions<CompanyContext> options)
            : base(options)
        {
        }

        public virtual DbSet<Department> Department { get; set; }
        public virtual DbSet<Employee> Employee { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
                #warning To protect potentially sensitive information in your connection string
                optionsBuilder.UseSqlServer("Server=vaio;Database=Company;Trusted_Connection=True;");
            }
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Department>(entity =>
            {
                entity.Property(e => e.Name)
                    .IsRequired()
                    .HasMaxLength(50)
                    .IsUnicode(false);
            });

            modelBuilder.Entity<Employee>(entity =>
            {
                entity.Property(e => e.Designation)
                    .IsRequired()
                    .HasMaxLength(25)
                    .IsUnicode(false);

                entity.Property(e => e.Name)
                    .IsRequired()
                    .HasMaxLength(100)
                    .IsUnicode(false);

                entity.HasOne(d => d.Department)
                    .WithMany(p => p.Employee)
                    .HasForeignKey(d => d.DepartmentId)
                    .OnDelete(DeleteBehavior.ClientSetNull)
                    .HasConstraintName("FK_Employee_Department");
            });

            OnModelCreatingPartial(modelBuilder);
        }

        partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
    }
}