diff --git a/MCTG/MCTGApp/MCTGApp.csproj b/MCTG/MCTGApp/MCTGApp.csproj
index 79a52db..f184388 100644
--- a/MCTG/MCTGApp/MCTGApp.csproj
+++ b/MCTG/MCTGApp/MCTGApp.csproj
@@ -7,10 +7,6 @@
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
-  <ItemGroup>
-    <None Include="..\.editorconfig" Link=".editorconfig" />
-  </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\MCTGLib\MCTGLib.csproj" />
   </ItemGroup>
diff --git a/MCTG/MCTGApp/Program.cs b/MCTG/MCTGApp/Program.cs
index 021e938..57a3a18 100644
--- a/MCTG/MCTGApp/Program.cs
+++ b/MCTG/MCTGApp/Program.cs
@@ -8,7 +8,7 @@ Console.WriteLine("Hello, World!\n");
 
 // TESTS:
 
-// tests on Recipe class
+Console.WriteLine("tests on Recipe class:");
 BaseItem r1 = new Recipe("A recipe...");
 
 r1.DisplayItem();
@@ -17,24 +17,30 @@ r1.DisplayDescription();
 
 Console.WriteLine();
 
-// tests on RecipeCollection class
+Console.WriteLine("tests on RecipeCollection class:");
 RecipeCollection rc = new RecipeCollection("A recipe collection...");
 for (uint i = 0; i < 10; i++)
 {
-    rc += new Recipe($"Recipe number {i} in the collection.");  // test overload + operator
+    rc += new Recipe($"Recipe number {i} in the collection.");
+    Console.WriteLine("test overload + operator");
 }
 
-try // test overload of [] operator
+Console.WriteLine("test overload of [] operator:");
+try
 {
     rc[2].DisplayId();
-    rc.GetById(1002);
+    rc.GetById(14).DisplayId();
 }
 catch (ArgumentNullException)
 {
     Console.Error.WriteLine("An index are incorrect!\n");
 }
+catch (Exception e)
+{
+    Console.Error.WriteLine("Exception thrown: {0}", e);
+}
 
-// test of multiple params constructor
+Console.WriteLine("test of multiple params constructor:");
 RecipeCollection rc2 = new RecipeCollection(
     new Recipe(),
     new Recipe(),
@@ -42,9 +48,8 @@ RecipeCollection rc2 = new RecipeCollection(
     new Recipe(),
     new Recipe());
 
-// test of Enumerable property
+Console.WriteLine("test of Enumerable property:");
 foreach (Recipe r in rc2)
 {
-    r.DisplayId();
-    r.DisplayDescription();
+    r.DisplayId(); Console.Write(" - ");
 }
diff --git a/MCTG/MCTGLib/BaseItem.cs b/MCTG/MCTGLib/BaseItem.cs
index f031d66..8d8cd81 100644
--- a/MCTG/MCTGLib/BaseItem.cs
+++ b/MCTG/MCTGLib/BaseItem.cs
@@ -1,6 +1,7 @@
 
 using System;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Model
 {
@@ -10,6 +11,8 @@ namespace Model
     /// </summary>
     public abstract class BaseItem : IDisplayable, IEquatable<BaseItem>
     {
+        #region Private Attributes
+
         /// <summary>
         /// The identifier of an Item.<br/>
         /// The first number correspond to the typs of the Item.
@@ -20,19 +23,28 @@ namespace Model
             init => _id = value;
         }
         protected uint _id;
-        
+
+        #endregion
+
+        #region Public Properties
 
         /// <summary>
         /// A short description of the Item. Useful to know what this Item stand for.
         /// </summary>
         public string Description { get; set; }
-   
+
+        #endregion
+
+        #region Constructors
 
         protected BaseItem(uint id, string description="Any Item.")
         {
             Id = id; Description = description;
         }
 
+        #endregion
+
+        #region Public Methods
 
         public override string ToString()
         {
@@ -43,7 +55,8 @@ namespace Model
                 $"______\n\n";
         }
 
-        // IDisplayable Implementation
+        #region IDisplayable Implementation
+
         public void DisplayId()
         {
             Console.WriteLine($".Id  -  {Id}");
@@ -59,27 +72,23 @@ namespace Model
             Console.WriteLine(this.ToString());
         }
 
-        // IEquatable<BaseItem> implementation
-        public bool Equals(BaseItem? other)
-        {
-            if (other != null)
-                return this.Id.Equals(other.Id);
+        #endregion
 
-            return false;
-        }
+        #region IEquatable<BaseItem> implementation
 
-        public override bool Equals(object? obj)
+        public int GetHashCode([DisallowNull] BaseItem obj)
         {
-            BaseItem? baseItem = obj as BaseItem;
-            if (baseItem == null) return false;
-            if (baseItem == this) return true;
-
-            return this.Id.Equals(baseItem.Id);
+            return obj.Id.GetHashCode() + obj.Description.GetHashCode();
         }
 
-        public override int GetHashCode()
+        public bool Equals(BaseItem? other)
         {
-            return this.Id.GetHashCode();
+            if (other == null) return false;
+            return (this.Id == other.Id) && (this.Description == other.Description);
         }
+
+        #endregion
+
+        #endregion
     }
 }
diff --git a/MCTG/MCTGLib/Recipe.cs b/MCTG/MCTGLib/Recipe.cs
index 2ab5420..f5cb00d 100644
--- a/MCTG/MCTGLib/Recipe.cs
+++ b/MCTG/MCTGLib/Recipe.cs
@@ -11,6 +11,7 @@ namespace Model
     {
         #region Private Attributes
 
+        private const int CAT_ITEM = 1;
         private static uint _idCreator = 0; // stand for the creation of a new id. It is incremented each time a new Recipe is instantiated.
         private string title = "";
 
@@ -57,9 +58,11 @@ namespace Model
         /// </summary>
         private static uint ComputeId()
         {
-            uint dec = 0, id = _idCreator;
-            while ((_idCreator / (Math.Pow(10, dec)) > 10)) dec++;
-            id += 1 * (uint)(Math.Pow(10, dec));
+            uint dec = 1;
+            while ((_idCreator / (Math.Pow(10, dec)) >= 1)) dec++;
+
+            uint id = (CAT_ITEM * (uint)(Math.Pow(10, dec))) + _idCreator++;
+            Console.WriteLine("[recipe] new computed id: {0}", id);
 
             return id;
         }
diff --git a/MCTG/MCTGLib/RecipeCollection.cs b/MCTG/MCTGLib/RecipeCollection.cs
index f93227d..c9ed6be 100644
--- a/MCTG/MCTGLib/RecipeCollection.cs
+++ b/MCTG/MCTGLib/RecipeCollection.cs
@@ -19,14 +19,15 @@ namespace Model
 
         #endregion
 
-
         #region Public Properties
+
         #region ICollection Implementation
 
         public int Count => _recipes.Count;
         public bool IsReadOnly => false;
 
         #endregion
+
         #endregion
 
         #region Constructors
@@ -51,9 +52,11 @@ namespace Model
         /// </summary>
         private static uint ComputeId()
         {
-            uint dec = 0, id = _idCreator;
-            while ((_idCreator / (Math.Pow(10, dec)) > 10)) dec++;
-            id += CAT_ITEM * (uint)(Math.Pow(10, dec));
+            uint dec = 1;
+            while ((_idCreator / (Math.Pow(10, dec)) >= 1)) dec++;
+
+            uint id = (CAT_ITEM * (uint)(Math.Pow(10, dec))) + _idCreator++;
+            Console.WriteLine("[recipe collection] new computed id: {0}", id);
 
             return id;
         }
@@ -76,7 +79,7 @@ namespace Model
             if (this._recipes is not List<Recipe>)
                 throw new InvalidCastException("Need to verify the type of the private attribute '_recipes'.");
 
-            return (this._recipes as List<Recipe>).Find(x => x.Id.Equals(Id));
+            return (this._recipes as List<Recipe>).Find(x => x.Id.Equals(id));
         }
 
         #region ICollection Implementation