(B) Update PatientMedicine, PatientDisease entities

Clinics.Backend/Domain/Entities/People/Patients/Patient.cs

-using Domain.Entities.People.Patients.Relations.PatientDiseases;
+using Domain.Entities.Medicals.Diseases;
+using Domain.Entities.Medicals.Medicines;
+using Domain.Entities.People.Patients.Relations.PatientDiseases;
 using Domain.Entities.People.Patients.Relations.PatientMedicines;
 using Domain.Entities.People.Shared;
 using Domain.Entities.People.Shared.GenderValues;
@@ -104,6 +106,46 @@ public sealed class Patient : Entity
     }
     #endregion
 
+    #region Add medicine
+    public void AddMedicine(Medicine medicine, int number)
+    {
+        PatientMedicine entry;
+
+        try
+        {
+            entry = PatientMedicine.Create(Id, medicine.Id, number);
+        }
+        catch
+        {
+            throw;
+        }
+        if (Medicines is null)
+            Medicines = [];
+        Medicines.Add(entry);
+    }
+    #endregion
+
+    #region Add disease
+    public void AddDisease (Disease disease)
+    {
+        PatientDisease entry;
+        try
+        {
+            entry = PatientDisease.Create(Id, disease.Id);
+        }
+        catch
+        {
+            throw;
+        }
+
+        if (Diseases is null)
+            Diseases = [];
+
+        Diseases.Add(entry);
+
+    }
+    #endregion
+
     #endregion
 
 }

Clinics.Backend/Domain/Entities/People/Patients/Relations/PatientDiseases/PatientDisease.cs

 using Domain.Entities.Medicals.Diseases;
+using Domain.Exceptions.InvalidValue;
 using Domain.Primitives;
 
 namespace Domain.Entities.People.Patients.Relations.PatientDiseases;
 
-public sealed class PatientDisease(int id) : Entity(id)
+public sealed class PatientDisease : Entity
 {
+    #region Private ctor
+    private PatientDisease(int id) : base(id)
+    {
+    }
+
+    private PatientDisease(int id, int patientId, int diseaseId) : base(id)
+    {
+        PatientId = patientId;
+        DiseaseId = diseaseId;
+    }
+    #endregion
 
     #region Properties
 
@@ -27,4 +39,17 @@ public sealed class PatientDisease(int id) : Entity(id)
     #endregion
 
     #endregion
+
+    #region Methods
+
+    #region Static factory
+    public static PatientDisease Create(int patientId, int diseaseId)
+    {
+        if (patientId <= 0 || diseaseId <= 0)
+            throw new InvalidValuesDomainException<PatientDisease>();
+        return new PatientDisease(0, patientId, diseaseId);
+    }
+    #endregion
+
+    #endregion
 }

Clinics.Backend/Domain/Entities/People/Patients/Relations/PatientMedicines/PatientMedicine.cs

 using Domain.Entities.Medicals.Medicines;
+using Domain.Exceptions.InvalidValue;
 using Domain.Primitives;
 
 namespace Domain.Entities.People.Patients.Relations.PatientMedicines;
 
-public sealed class PatientMedicine(int id) : Entity(id)
+public sealed class PatientMedicine : Entity
 {
+
+
+    #region Private ctor
+    private PatientMedicine(int id) : base(id)
+    {
+    }
+    private PatientMedicine(int id, int patientId, int medicineId, int number) : base(id)
+    {
+        PatientId = patientId;
+        MedicineId = medicineId;
+        Number = number;
+    }
+
+    #endregion
+
     #region Properties
 
     #region Patient
@@ -28,5 +44,18 @@ public sealed class PatientMedicine(int id) : Entity(id)
     #endregion
 
 
+    #endregion
+
+    #region Methods
+
+    #region Static factory
+    public static PatientMedicine Create(int patientId, int medicineId, int number)
+    {
+        if (patientId <= 0 || medicineId <= 0 || number <= 0)
+            throw new InvalidValuesDomainException<PatientMedicine>();
+        return new PatientMedicine(0, patientId, medicineId, number);
+    }
+    #endregion
+
     #endregion
 }