Первый шаг: проверка уникальности объекта

ArmoredCar/ArmoredCar/DrawningObjectArmCar.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.DirectoryServices.ActiveDirectory;
 using System.Drawing;
 using System.Linq;
 using System.Text;
@@ -34,7 +35,54 @@ namespace ArmoredCar
                 _armCar.DrawTransport(g);
         }
         public string GetInfo() => _armCar?.GetDataForSave();
-        public static IDrawningObject Create(string data) => new
-       DrawningObjectArmCar(data.CreateDrawningArmoredCar());
+        public static IDrawningObject Create(string data) => new DrawningObjectArmCar(data.CreateDrawningArmoredCar());
+
+        public bool Equals(IDrawningObject? other)
+        {
+            if (other == null)
+            {
+                return false;
+            }
+            var otherCar = other as DrawningObjectArmCar;
+            if (otherCar == null)
+            {
+                return false;
+            }
+            var car = _armCar.ArmoredCar;
+            var otherCarCar = otherCar._armCar.ArmoredCar;
+
+            if (car.GetType() != otherCarCar.GetType())
+                return false;
+
+            if (car.Speed != otherCarCar.Speed)
+            {
+                return false;
+            }
+            if (car.Weight != otherCarCar.Weight)
+            {
+                return false;
+            }
+            if (car.BodyColor != otherCarCar.BodyColor)
+            {
+                return false;
+            }
+            if (car is EntityTank tank && otherCarCar is EntityTank otherTank)
+            {
+                if (tank.DopColor != otherTank.DopColor)
+                {
+                    return false;
+                }
+                if (tank.TowerWeapon != otherTank.TowerWeapon)
+                {
+                    return false;
+                }
+                if (tank.AMachineGun != otherTank.AMachineGun)
+                {
+                    return false;
+                }
+            }        
+            return true;
+        }
+
     }
 }

ArmoredCar/ArmoredCar/IDrawningObject.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 
 namespace ArmoredCar
 {
-    internal interface IDrawningObject
+    internal interface IDrawningObject : IEquatable<IDrawningObject>
     {
         /// <summary>
         /// Шаг перемещения объекта

ArmoredCar/ArmoredCar/MapWithSetArmoredCarsGeneric.cs

@@ -8,7 +8,7 @@ using System.Threading.Tasks;
 namespace ArmoredCar
 {
     internal class MapWithSetArmoredCarsGeneric<T, U>
-        where T : class, IDrawningObject
+        where T : class, IDrawningObject, IEquatable<T>
         where U : AbstractMap
     {
         /// <summary>

ArmoredCar/ArmoredCar/SetArmoredCarsGeneric.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 namespace ArmoredCar
 {
     internal class SetArmoredCarsGeneric<T>
-        where T : class
+        where T : class, IEquatable<T>
     {
         /// <summary>
         /// Список объектов, которые храним
@@ -43,13 +43,19 @@ namespace ArmoredCar
         /// <param name="position">Позиция</param>
         /// <returns></returns>
         public int Insert(T armoredCar, int position)
-        {
+        {                
             if (Count >= _maxCount)
                 throw new StorageOverflowException(Count);
 
             if (position < 0 || position >= _maxCount)
                 return -1;
 
+            // проверка на уникальность
+            if (_places.Contains(armoredCar))
+            {
+                return -1;
+            }
+
             _places.Insert(position, armoredCar);         
             return position;
         }