diff --git a/Sources/Stim.Model/Game.cs b/Sources/Stim.Model/Game.cs
index 7ef01fb..800f092 100644
--- a/Sources/Stim.Model/Game.cs
+++ b/Sources/Stim.Model/Game.cs
@@ -7,12 +7,12 @@ using System.Text;
 namespace Model
 {
     [DataContract]
-    public class Game : INotifyPropertyChanged, IEquatable<Game>
+    public sealed class Game : INotifyPropertyChanged, IEquatable<Game>
     {
         [DataMember]
         public string Name
         {
-            get => name ?? "Default";
+            get => name;
             private set
             {
                 if (string.IsNullOrWhiteSpace(value)) name="Default";
@@ -28,7 +28,7 @@ namespace Model
         [DataMember]
         public string Description
         {
-            get => description ?? "Pas de description";
+            get => description;
             private set
             {
                 if (string.IsNullOrWhiteSpace(value)) return;
@@ -60,7 +60,7 @@ namespace Model
         [DataMember]
         public string Cover
         {
-            get => cover ?? "no_cover.png";
+            get => cover;
             private set
             {
                 if (string.IsNullOrWhiteSpace(value)) cover="no_cover.png";
@@ -101,7 +101,7 @@ namespace Model
 
         [DataMember]
         public string Lien { 
-            get => lien ?? "Pas de lien";
+            get => lien;
             private set
             {
                 if (string.IsNullOrWhiteSpace(value)) return;
diff --git a/Sources/Stim.Model/User.cs b/Sources/Stim.Model/User.cs
index e26b0fc..9988a45 100644
--- a/Sources/Stim.Model/User.cs
+++ b/Sources/Stim.Model/User.cs
@@ -8,7 +8,7 @@ using System.Text.RegularExpressions;
 namespace Model
 {
     [DataContract]
-    public class User : INotifyPropertyChanged , IEquatable<User>
+    public sealed class User : INotifyPropertyChanged , IEquatable<User>
     {
         [DataMember]
         public string? Username
@@ -63,7 +63,7 @@ namespace Model
             private set
             {
                 Regex rg = new Regex("^(?=.*[A-Za-z])(?=.*[0-9@$!%*#?&])[A-Za-z-0-9@$!%*#?&]{8,}$");
-                if (string.IsNullOrWhiteSpace(value) || !rg.IsMatch(value)) throw new ArgumentNullException("password");
+                if (string.IsNullOrWhiteSpace(value) || !rg.IsMatch(value)) throw new ArgumentNullException(value);
                 else
                 {
                     password = value;
diff --git a/Sources/TestProject1/TestGame.cs b/Sources/TestProject1/TestGame.cs
index 2d81b34..e3556ea 100644
--- a/Sources/TestProject1/TestGame.cs
+++ b/Sources/TestProject1/TestGame.cs
@@ -172,7 +172,7 @@ namespace Test
         {
             Game game = new("name", "description", 2012, new List<String> { "1", "2", "3" }, "cover", "www.link.com");
             Game game2 = new("name2", "description", 2020, new List<String> { "1" }, "cover2", "www.link.com");
-            Game game3 = null;
+            Game? game3 = null;
             string game4 = "";
 
             Assert.False(game.Equals(game2 as Game));
diff --git a/Sources/TestProject1/TestUser.cs b/Sources/TestProject1/TestUser.cs
index 6b75a09..0f65799 100644
--- a/Sources/TestProject1/TestUser.cs
+++ b/Sources/TestProject1/TestUser.cs
@@ -100,8 +100,7 @@ namespace Test
             User user = new("userimage", "username", "biographie", "adresse.mail@gmail.com", "Azerty123*");
             User user2 = new("userimage", "username2", "biographie", "adresse.mail@gmail.com", "Azerty123*");
             User user3 = new("userimage", "username", "biographie", "adresse.mail@gmail.com", "Azerty123*");
-            User user4 = null;
-            string user5 = "";
+            User? user4 = null;
 
             Assert.False(user.Equals(user2 as User));
             Assert.False(user.Equals(user2 as object));