New: better Exception Handling

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Components/Layout/MainLayout.razor

@@ -1,4 +1,9 @@
-@inherits LayoutComponentBase
+@using Services
+@inherits LayoutComponentBase
+@implements IDisposable
+@rendermode RenderMode.InteractiveServer
+@inject IErrorService ErrorService
+
 
 <div class="page">
     <div class="sidebar">
@@ -7,6 +12,13 @@
 
     <main>
         <article class="content px-4">
+            @if(ErrorService.ex != null) {
+                <div class="alert alert-danger m-3" role="alert">
+                    @ErrorService.ex.Message
+                    <button type="button" class="btn-close float-end" aria-label="Close" @onclick="DismissError"></button>
+                </div>
+            }
+            
             @Body
         </article>
     </main>
@@ -17,3 +29,20 @@
     <a href="." class="reload">Reload</a>
     <span class="dismiss">🗙</span>
 </div>
+
+@code {
+    protected override void OnInitialized()
+    {
+        ErrorService.OnChange += StateHasChanged;
+    }
+
+    private void DismissError()
+    {
+        ErrorService.ex = null;
+    }
+
+    public void Dispose()
+    {
+        ErrorService.OnChange -= StateHasChanged;
+    }
+}

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Components/Pages/ErrorTest.razor

@@ -0,0 +1,18 @@
+@page "/ErrorTest"
+@using Microsoft.Data.SqlClient
+@using Services
+@inject IErrorService ErrorService
+
+<PageTitle>Error Test</PageTitle>
+
+<h1>Error Page</h1>
+
+<button @onclick="SetError" class="btn btn-primary">Set Error</button>
+
+@code {
+
+    private void SetError() {
+        ErrorService.ex = new Exception("Hello World");
+    }
+
+}

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Components/Pages/Home.razor

@@ -1,7 +1,9 @@
 @page "/"
 @using Models
 @using Services
+@using System.Runtime.InteropServices
 @inject IRentService RentService
+@inject IErrorService ErrorService
 
 <PageTitle>Home</PageTitle>
 
@@ -45,9 +47,11 @@
 
     protected override void OnInitialized()
     {
-        _vehicles = RentService.GetAvailableCars();
+        try {
-        Console.WriteLine("VC" +  _vehicles.Count);
+            _vehicles = RentService.GetAvailableCars();
-        @* return Task.CompletedTask; *@
+        } catch (Exception e) {
+            ErrorService.ex = e;
+        }
     }
 
 }

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Components/Pages/Rent.razor

@@ -1,8 +1,10 @@
 @page "/rent"
 @using Models
 @using Services
+@using System.Runtime.InteropServices
 @inject IRentService RentService
 @inject NavigationManager NavigationManager
+@inject IErrorService ErrorService
 
 <PageTitle>Rent</PageTitle>
 
@@ -41,15 +43,22 @@
 
     protected override void OnInitialized()
     {
-        _vehicles = RentService.GetAvailableCars();
+        try {
-        _customers = RentService.GetCustomers();
+            _vehicles = RentService.GetAvailableCars();
+            _customers = RentService.GetCustomers();
+        } catch (Exception e) {
+            ErrorService.ex = e;
+        }
     }
 
     private Task RentCar()
     {
-        RentService.RentCar(_customerId, _vehicleId, _from, _thru);
+        try {
-        Console.WriteLine("Rented Car");
+            RentService.RentCar(_customerId, _vehicleId, _from, _thru);
-        NavigationManager.NavigateTo("/");
+            NavigationManager.NavigateTo("/");
+        } catch (Exception e) {
+            ErrorService.ex = e;
+        }
         return Task.CompletedTask;
     }
 }

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Components/Pages/Rollback.razor

@@ -2,6 +2,7 @@
 @using Models
 @using Services
 @inject IRollbackService RollbackService
+@inject IErrorService ErrorService
 
 <PageTitle>Rollback</PageTitle>
 
@@ -12,7 +13,11 @@
 
 @code {
     private Task PerformRollback() {
-        RollbackService.ResetToDefaults();
+        try {
+            RollbackService.ResetToDefaults();
+        } catch (Exception e) {
+            ErrorService.ex = e;
+        }
         return Task.CompletedTask;
     }
 }

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Configuration/ServiceCollectionExtension.cs

@@ -17,6 +17,7 @@ public static class ServiceCollectionExtension
 
         services.Services.AddScoped<IRentService, RentService>();
         services.Services.AddScoped<IRollbackService, RollbackService>();
+        services.Services.AddScoped<IErrorService, ErrorService>();
         return services;
     }
 }

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Services/ErrorService.cs

@@ -0,0 +1,30 @@
+using System.Data;
+using Configuration;
+using Microsoft.Data.SqlClient;
+using Models;
+
+namespace Services
+{
+    public interface IErrorService
+    {
+        Exception? ex { get; set; }
+        event Action? OnChange;
+    }
+
+    public class ErrorService : IErrorService
+    {
+        private Exception? _ex;
+        public Exception? ex
+        {
+            get => _ex;
+            set
+            {
+                _ex = value;
+                NotifyStateChanged();
+            }
+        }
+
+        public event Action? OnChange;
+        private void NotifyStateChanged() => OnChange?.Invoke();
+    }
+}

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Services/RentService.cs

@@ -17,22 +17,16 @@ namespace Services
         public List<Vehicle> GetAvailableCars()
         {
             List<Vehicle> vehicles = new List<Vehicle>();
-            try
-            {
-                using SqlConnection conn = sqlConnectionFactory.CreateSqlConnection();
-                string sql = "SELECT * FROM v_VerfuegbareFahrzeuge;";
-                SqlCommand cmd = new SqlCommand(sql, conn);
 
-                using SqlDataReader reader = cmd.ExecuteReader();
+            using SqlConnection conn = sqlConnectionFactory.CreateSqlConnection();
+            string sql = "SELECT * FROM v_VerfuegbareFahrzeuge;";
+            SqlCommand cmd = new SqlCommand(sql, conn);
 
-                while (reader.Read())
+            using SqlDataReader reader = cmd.ExecuteReader();
-                {
+
-                    vehicles.Add(Vehicle.FromReader(reader));
+            while (reader.Read())
-                }
-            }
-            catch (Exception e)
             {
-                Console.WriteLine(e);
+                vehicles.Add(Vehicle.FromReader(reader));
             }
 
             return vehicles;
@@ -41,45 +35,34 @@ namespace Services
         public List<Customer> GetCustomers()
         {
             List<Customer> customers = new List<Customer>();
-            try
+            
+            using SqlConnection conn = sqlConnectionFactory.CreateSqlConnection();
+            string sql = "SELECT * FROM Customer;";
+            SqlCommand cmd = new SqlCommand(sql, conn);
+
+            using SqlDataReader reader = cmd.ExecuteReader();
+
+            while (reader.Read())
             {
-                using SqlConnection conn = sqlConnectionFactory.CreateSqlConnection();
+                customers.Add(Customer.FromReader(reader));
-                string sql = "SELECT * FROM Customer;";
-                SqlCommand cmd = new SqlCommand(sql, conn);
-
-                using SqlDataReader reader = cmd.ExecuteReader();
-
-                while (reader.Read())
-                {
-                    customers.Add(Customer.FromReader(reader));
-                }
             }
-            catch (Exception e)
+        
-            {
-                Console.WriteLine(e);
-            }
-
             return customers;
         }
 
         public void RentCar(long customerId, long vehicleId, DateTime start, DateTime end)
         {
-            try
+        
-            {
+            using SqlConnection conn = sqlConnectionFactory.CreateSqlConnection();
-                using SqlConnection conn = sqlConnectionFactory.CreateSqlConnection();
+            using SqlCommand cmd = new SqlCommand("sp_MieteFahrzeug", conn);
-                using SqlCommand cmd = new SqlCommand("sp_MieteFahrzeug", conn);
+            cmd.CommandType = CommandType.StoredProcedure;
-                cmd.CommandType = CommandType.StoredProcedure;
 
-                cmd.Parameters.AddWithValue("@KundeID", customerId);
+            cmd.Parameters.AddWithValue("@KundeID", customerId);
-                cmd.Parameters.AddWithValue("@FahrzeugID", vehicleId);
+            cmd.Parameters.AddWithValue("@FahrzeugID", vehicleId);
-                cmd.Parameters.AddWithValue("@Start", start);
+            cmd.Parameters.AddWithValue("@Start", start);
-                cmd.Parameters.AddWithValue("@Ende", end);
+            cmd.Parameters.AddWithValue("@Ende", end);
 
-                cmd.ExecuteNonQuery();
+            cmd.ExecuteNonQuery();
-            }catch (Exception ex)
-            {
-                Console.WriteLine(ex);
-            }
         }
     }
 }

Einheit_4/2025_5BHITN_Konstantin_Hintermayer_smarterrent/Services/RollbackService.cs

@@ -14,24 +14,17 @@ namespace Services
     {
         public void ResetToDefaults()
         {
-            try
+            using SqlConnection conn = sqlConnectionFactory.CreateSqlConnection();
-            {
-                using SqlConnection conn = sqlConnectionFactory.CreateSqlConnection();
 
-                string sql = @"
+            string sql = @"
-    USE [master];
+USE [master];
-    ALTER DATABASE [2025_5bhitn_konstantin_hintermayer_smarter_rentDB] SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
+ALTER DATABASE [2025_5bhitn_konstantin_hintermayer_smarter_rentDB] SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
-    RESTORE DATABASE [2025_5bhitn_konstantin_hintermayer_smarter_rentDB] FROM DATABASE_SNAPSHOT = '2025_5bhitn_konstantin_hintermayer_smarter_rentDB_snapshot';
+RESTORE DATABASE [2025_5bhitn_konstantin_hintermayer_smarter_rentDB] FROM DATABASE_SNAPSHOT = '2025_5bhitn_konstantin_hintermayer_smarter_rentDB_snapshot';
-    ALTER DATABASE [2025_5bhitn_konstantin_hintermayer_smarter_rentDB] SET MULTI_USER;";
+ALTER DATABASE [2025_5bhitn_konstantin_hintermayer_smarter_rentDB] SET MULTI_USER;";
 
-                using SqlCommand cmd = new SqlCommand(sql, conn);
+            using SqlCommand cmd = new SqlCommand(sql, conn);
 
-                cmd.ExecuteNonQuery();
+            cmd.ExecuteNonQuery();
-            }
-            catch (Exception ex)
-            {
-                Console.WriteLine(ex);
-            }
         }
     }
 }