wrong way to multi multi db

Domain/Cource.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.ComponentModel.DataAnnotations;
+
+
+namespace Domain
+{
+    public class Cource
+    {
+        public int CourceId { get; set; }
+        
+        // if not required, use nullable int - int?. Dadabase pics it up
+        // always specify foregin key manualy
+        public int SubjectId { get; set; }
+        public Subject Subject { get; set; }
+
+        public virtual List<Person> Persons { get; set; } = new List<Person>();
+    }
+}

Domain/Domain.csproj

@@ -41,8 +41,12 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Cource.cs" />
+    <Compile Include="Enums\PersonType.cs" />
     <Compile Include="Person.cs" />
+    <Compile Include="PersonCources.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="Subject.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 

Domain/Enums/PersonType.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Domain.Enums
+{
+    class PersonType
+    {
+        public enum PersonTypeEnum {
+            Student,
+            Teacher
+        }
+    }
+}

Domain/Person.cs

@@ -20,6 +20,8 @@ namespace Domain
         [Required]
         public string LastName { get; set; }
 
+        public virtual List<Cource> Courses { get; set; }
+
         #region NotMaped
         public string FirstLastName => $"{FirstName} {LastName}";
         public string LastFirstName => $"{LastName} {FirstName}";

Domain/PersonCources.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Domain
+{
+    public class PersonCources
+    {
+        public int PersonCourcesId { get; set; }
+
+        public int PersonId { get; set; }
+        public Person Person { get; set; }
+
+        public int CourceId { get; set; }
+        public Cource Cource { get; set; }
+    }
+}

Domain/Subject.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.ComponentModel.DataAnnotations;
+
+
+namespace Domain
+{
+    class Subject
+    {
+        public int SubjectId { get; set; }
+
+        [MaxLength(128)]
+        public string SubjectName { get; set; }
+
+        // use virtual to allow entity framework lazy loading
+        public virtual List<Cource> Cources { get; set; } = new List<Cource>();
+    }
+}