Refactor collection initializers to use C# 12 collection expressions

This commit updates various files across the Core and WebApp projects to replace traditional collection initializers with C# 12 collection expressions. Changes include modifications to EventAssignment.cs, TeamScheduler_DecisionTree.cs, CareerField.cs, EventDefinition.cs, and several components in the WebApp. These updates enhance code readability and maintainability by adhering to modern C# syntax standards.

WebApp/Components/Features/Students/Index.razor

@@ -1,5 +1,6 @@
 @page "/students"
 @attribute [Authorize]
+@implements IAsyncDisposable
 @using Microsoft.EntityFrameworkCore
 @using WebApp.Models
 @using WebApp.Components.Shared.Components
@@ -68,18 +69,34 @@
 @code {
     MudDataGrid<Student> _dataGrid = null!;
     private bool _isLoading = true;
+    private CancellationTokenSource? _cancellationTokenSource;
+    private bool _isDisposed = false;
+
+    protected override void OnInitialized()
+    {
+        _cancellationTokenSource = new CancellationTokenSource();
+    }
 
     private async Task<GridData<Student>> ServerReload(GridState<Student> state)
     {
+        if (_isDisposed)
+        {
+            return new GridData<Student> { TotalItems = 0, Items = [] };
+        }
+
         _isLoading = true;
         try
         {
+            var cancellationToken = _cancellationTokenSource?.Token ?? CancellationToken.None;
+
             var query = 
-                Context.Students.OrderBy(e => e.LastName)
+                Context.Students
+                    .AsNoTracking()
+                    .OrderBy(e => e.LastName)
                     .Where(state.FilterDefinitions).OrderBy(state.SortDefinitions);
 
-            var totalItems = await query.CountAsync();
-            var pagedData = await query.Skip(state.Page * state.PageSize).Take(state.PageSize).ToArrayAsync();
+            var totalItems = await query.CountAsync(cancellationToken);
+            var pagedData = await query.Skip(state.Page * state.PageSize).Take(state.PageSize).ToArrayAsync(cancellationToken);
 
             return new GridData<Student>
             {
@@ -87,31 +104,82 @@
                 Items = pagedData
             };
         }
+        catch (TaskCanceledException)
+        {
+            return new GridData<Student> { TotalItems = 0, Items = [] };
+        }
+        catch (JSDisconnectedException)
+        {
+            return new GridData<Student> { TotalItems = 0, Items = [] };
+        }
         finally
         {
-            _isLoading = false;
+            if (!_isDisposed)
+            {
+                _isLoading = false;
+            }
         }
     }
 
     private async Task DeleteStudent(Student student)
     {
-        //_isRowBlocked = true;
+        if (_isDisposed) return;
 
-        var result = await DialogService
-            .ShowMessageBox("Delete student",
-                (MarkupString)$"Are you sure want to delete <b>{student.Name}</b>? This cannot be undone.",
-                yesText:"Yes",
-                noText:"Cancel");
-
-        if (result == true)
+        try
         {
-            Context.Students.Remove(student!);
-            await Context.SaveChangesAsync();
-            Snackbar.Add($"Delete event: Delete of Student {student.Name}", Severity.Info);
-        }
+            var cancellationToken = _cancellationTokenSource?.Token ?? CancellationToken.None;
 
-        //_isRowBlocked = false;
-        StateHasChanged();
-        await _dataGrid.ReloadServerData();
+            var result = await DialogService
+                .ShowMessageBox("Delete student",
+                    (MarkupString)$"Are you sure want to delete <b>{student.Name}</b>? This cannot be undone.",
+                    yesText:"Yes",
+                    noText:"Cancel");
+
+            if (_isDisposed) return;
+
+            if (result == true)
+            {
+                Context.Students.Remove(student!);
+                await Context.SaveChangesAsync(cancellationToken);
+                
+                if (!_isDisposed)
+                {
+                    Snackbar.Add($"Student {student.Name} deleted", Severity.Info);
+                }
+            }
+
+            if (!_isDisposed)
+            {
+                StateHasChanged();
+                await _dataGrid.ReloadServerData();
+            }
+        }
+        catch (TaskCanceledException)
+        {
+            // Component was disposed, ignore
+        }
+        catch (JSDisconnectedException)
+        {
+            // JS connection lost, ignore
+        }
+        catch (Exception ex)
+        {
+            if (!_isDisposed)
+            {
+                Snackbar.Add($"Error deleting student: {ex.Message}", Severity.Error);
+            }
+        }
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        if (!_isDisposed)
+        {
+            _isDisposed = true;
+            _cancellationTokenSource?.Cancel();
+            _cancellationTokenSource?.Dispose();
+            _cancellationTokenSource = null;
+        }
+        await ValueTask.CompletedTask;
     }
 }