Entities

src/Plus/Domain/Entities/Entity.cs

+using System;
+using System.Collections.Generic;
+
+namespace Plus.Domain.Entities
+{
+    [Serializable]
+    public abstract class Entity : Entity<int>, IEntity
+    {
+
+    }
+
+    [Serializable]
+    public abstract class Entity<TPrimaryKey> : IEntity<TPrimaryKey>
+    {
+        public virtual TPrimaryKey Id { get; set; }
+
+        public virtual bool IsTransient()
+        {
+            return EqualityComparer<TPrimaryKey>.Default.Equals(Id, default);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (obj == null || !(obj is Entity<TPrimaryKey>))
+            {
+                return false;
+            }
+
+            if (ReferenceEquals(this, obj))
+            {
+                return true;
+            }
+
+            Entity<TPrimaryKey> entity = (Entity<TPrimaryKey>)obj;
+            if (IsTransient() && entity.IsTransient())
+            {
+                return false;
+            }
+
+            Type type = GetType();
+            Type type2 = entity.GetType();
+            if (!type.IsAssignableFrom(type2) && !type2.IsAssignableFrom(type))
+            {
+                return false;
+            }
+
+            return Id.Equals(entity.Id);
+        }
+
+        public override int GetHashCode()
+        {
+            return Id.GetHashCode();
+        }
+
+        public static bool operator ==(Entity<TPrimaryKey> left, Entity<TPrimaryKey> right)
+        {
+            if (Equals(left, null))
+            {
+                return Equals(right, null);
+            }
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(Entity<TPrimaryKey> left, Entity<TPrimaryKey> right)
+        {
+            return !(left == right);
+        }
+
+        public override string ToString()
+        {
+            return $"[{GetType().Name} {Id}]";
+        }
+    }
+}
\ No newline at end of file

src/Plus/Domain/Entities/IEntity.cs

 namespace Plus.Domain.Entities
 {
-    public interface IEntity
+    public interface IEntity : IEntity<int>
     {
+
     }
 }
\ No newline at end of file