Update lazy load pattern examples

Author: nemanjarogic

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/Executor.cs

@@ -17,4 +17,4 @@ public override void Execute()
         ValueHolderExecutor.Execute();
         VirtualProxyExecutor.Execute();
     }
-}
+}

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/GhostsExample/DomainObject.cs

@@ -9,10 +9,8 @@ protected DomainObject(int id)
         Id = id;
     }
 
-    public int Id { get; set; }
-
+    public int Id { get; init; }
     public bool IsGhost => _status == LoadStatus.Unloaded;
-
     public bool IsLoaded => _status == LoadStatus.Loaded;
 
     /// <summary>

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/GhostsExample/GhostCollege.cs

@@ -10,9 +10,9 @@
 /// </summary>
 public class GhostCollege : DomainObject
 {
-    private string _missionStatement;
-    private int _numberOfStudents;
-    private Library _library;
+    private string? _missionStatement;
+    private int? _numberOfStudents;
+    private Library? _library;
 
     public GhostCollege(int id)
         : base(id)
@@ -26,7 +26,7 @@ public string MissionStatement
         get
         {
             LoadIfNecessary();
-            return _missionStatement;
+            return _missionStatement!;
         }
         set => _missionStatement = value;
     }
@@ -36,7 +36,7 @@ public int NumberOfStudents
         get
         {
             LoadIfNecessary();
-            return _numberOfStudents;
+            return _numberOfStudents!.Value;
         }
         set => _numberOfStudents = value;
     }
@@ -46,7 +46,7 @@ public Library Library
         get
         {
             LoadIfNecessary();
-            return _library;
+            return _library!;
         }
         set => _library = value;
     }
@@ -73,4 +73,4 @@ protected override void ApplyLoadedData(object[] dataRow)
         _numberOfStudents = (int)dataRow[1];
         _library = (Library)dataRow[2];
     }
-}
+}

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/GhostsExample/GhostsExecutor.cs

@@ -18,4 +18,4 @@ public static void Execute()
         Console.WriteLine("\nGive me more details about the college!");
         college.ShowDetails();
     }
-}
+}

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/GhostsExample/LoadStatus.cs

@@ -5,4 +5,4 @@ public enum LoadStatus
     Unloaded,
     Loading,
     Loaded,
-}
+}

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/LazyInitializationExample/LazyCollege.cs

@@ -2,7 +2,7 @@
 
 public class LazyCollege
 {
-    private Library _library;
+    private Library? _library;
 
     public Library Library
     {

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/LazyInitializationExample/LazyInitializationExecutor.cs

@@ -16,4 +16,4 @@ public static void Execute()
         Console.WriteLine("\nGive me more details about the college!");
         dotNetCollege.ShowDetails();
     }
-}
+}

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/Library.cs

@@ -12,11 +12,8 @@ public Library()
         NumberOfBooks = 10000;
     }
 
-    public string Name { get; set; }
-
-    public DateTime EstablishmentDate { get; set; }
-
-    public string Address { get; set; }
-
-    public int NumberOfBooks { get; set; }
-}
+    public string Name { get; }
+    public DateTime EstablishmentDate { get; }
+    public string Address { get; }
+    public int NumberOfBooks { get; }
+}

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/ValueHolderExample/IValueLoader.cs

@@ -1,6 +1,6 @@
 namespace LazyLoadLibrary.ValueHolderExample;
 
-public interface IValueLoader<T>
+public interface IValueLoader<out T>
 {
     T Load();
-}
+}

src/AdditionalPatterns/LazyLoad/LazyLoadLibrary/ValueHolderExample/ValueHolder.cs

@@ -2,15 +2,15 @@
 
 /// <summary>
 /// A value holder is a generic object that handles the lazy loading behavior
-/// and appears in place of the object’s data fields.
+/// and appears in place of the object's data fields.
 /// When clients need to access it, they simply ask the value holder for its value.
 /// That is the moment when the value gets loaded (from a database or similar source).
 /// </summary>
 /// <typeparam name="T">Value type.</typeparam>
 public class ValueHolder<T>
 {
     private readonly IValueLoader<T> _loader;
-    private T _value;
+    private T? _value;
 
     public ValueHolder(IValueLoader<T> loader)
     {
@@ -29,4 +29,4 @@ public T Value
             return _value;
         }
     }
-}
+}