diff --git a/Blazor/Blazor/Models/AdministratorModel.cs b/Blazor/Blazor/Models/AdministratorModel.cs
index 89e5042..0fdf7c4 100644
--- a/Blazor/Blazor/Models/AdministratorModel.cs
+++ b/Blazor/Blazor/Models/AdministratorModel.cs
@@ -1,6 +1,7 @@
 using Microsoft.AspNetCore.Cryptography.KeyDerivation;
 using Microsoft.AspNetCore.Identity;
 using System.Security.Cryptography;
+using System.ComponentModel.DataAnnotations;
 using System.Text;
 
 namespace Blazor.Models;
@@ -8,7 +9,12 @@ namespace Blazor.Models;
 public class AdministratorModel 
 {
     public int Id { get; set; }
+
+    [Required(ErrorMessage = "Username is required")]
+    [StringLength(50, ErrorMessage = "Username is too long.")]
     public string Username { get; set; }
+
+    [Required(ErrorMessage = "Password is required")]
     public string HashedPassword { get; set; }
 
     public void HashPassword(string password)
diff --git a/Blazor/Blazor/Models/AnswerModel.cs b/Blazor/Blazor/Models/AnswerModel.cs
index ec2d19c..88753e9 100644
--- a/Blazor/Blazor/Models/AnswerModel.cs
+++ b/Blazor/Blazor/Models/AnswerModel.cs
@@ -1,9 +1,14 @@
-namespace Blazor.Models;
+using System.ComponentModel.DataAnnotations;
+
+namespace Blazor.Models;
 
 public class AnswerModel
 
 {
     public int Id { get; set; }
+
+    [Required(ErrorMessage = "Content is required")]
+    [StringLength(40, ErrorMessage = "Content is too long.")]
     public string? Content { get; set; }
     public int? IdQuestion { get; set; }
     public AnswerModel(int id)
diff --git a/Blazor/Blazor/Models/PlayerModel.cs b/Blazor/Blazor/Models/PlayerModel.cs
index 43c37a0..7cdd986 100644
--- a/Blazor/Blazor/Models/PlayerModel.cs
+++ b/Blazor/Blazor/Models/PlayerModel.cs
@@ -1,4 +1,5 @@
 using Microsoft.AspNetCore.Cryptography.KeyDerivation;
+using System.ComponentModel.DataAnnotations;
 using System.Security.Cryptography;
 using System.Text;
 
@@ -7,7 +8,12 @@ namespace Blazor.Models;
 public class PlayerModel
 {
     public int Id { get; set; }
+
+    [Required(ErrorMessage = "Nickname is required")]
+    [StringLength(50, ErrorMessage = "Nickname is too long.")]
     public string Nickname { get; set; }
+
+    [Required(ErrorMessage = "Password is required")]
     public string HashedPassword { get; set; }
 
     public void HashPassword(string password)
diff --git a/Blazor/Blazor/Models/QuestionModel.cs b/Blazor/Blazor/Models/QuestionModel.cs
index 4089498..2c1e606 100644
--- a/Blazor/Blazor/Models/QuestionModel.cs
+++ b/Blazor/Blazor/Models/QuestionModel.cs
@@ -1,9 +1,15 @@
 namespace Blazor.Models;
+using System.ComponentModel.DataAnnotations;
 
 public class QuestionModel
 {
     public int Id { get; set; }
+
+    [Required(ErrorMessage = "Content is required")]
+    [StringLength(50, ErrorMessage = "Content is too long.")]
     public string Content { get; set; }
+
+    [Required(ErrorMessage = "Chapter is required")]
     public int IdChapter { get; set; }
     public int IdAnswerGood { get; set; }
     public int Difficulty { get; set; }
diff --git a/Blazor/Blazor/Services/DataLocalService.cs b/Blazor/Blazor/Services/DataLocalService.cs
index 8b5542c..fd3cd03 100644
--- a/Blazor/Blazor/Services/DataLocalService.cs
+++ b/Blazor/Blazor/Services/DataLocalService.cs
@@ -62,7 +62,6 @@ namespace Blazor.Services
             await _localStorage.SetItemAsync("data", currentData);
         }
 
-
         public async Task Add(ChapterModel model)
         {
             // Get the current data
@@ -77,7 +76,6 @@ namespace Blazor.Services
                 Id = model.Id,
                 Name = model.Name
             });
-
           
             // Save the data
             await _localStorage.SetItemAsync("data", currentData);