nuclex-shared-dotnet/Nuclex.Avalonia
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Made the TPageEnumeration a value type so the multi page view model can start out with 'null' and switch to the initial page after the main window loads

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Markus Ewald 2026-04-28 09:31:04 +02:00 • committed by Markus Ewald
commit 7d98ba1e0d
3 changed files with 17 additions and 10 deletions
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4
Properties/AssemblyInfo.cs
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@ -27,7 +27,7 @@ using System.Runtime.InteropServices;
[assembly: AssemblyProduct("Nuclex.Avalonia")] [assembly: AssemblyProduct("Nuclex.Avalonia")]
[assembly: AssemblyDescription("Lean and elegant MVVM library with extras for Avalonia")] [assembly: AssemblyDescription("Lean and elegant MVVM library with extras for Avalonia")]
[assembly: AssemblyCompany("Nuclex Development Labs")] [assembly: AssemblyCompany("Nuclex Development Labs")]
[assembly: AssemblyCopyright("Copyright © Markus Ewald / Nuclex Development Labs 2002-2025")] [assembly: AssemblyCopyright("Copyright © Markus Ewald / Nuclex Development Labs 2002-2026")]
[assembly: AssemblyTrademark("")] [assembly: AssemblyTrademark("")]
[assembly: AssemblyCulture("")] [assembly: AssemblyCulture("")]
@ -46,4 +46,4 @@ using System.Runtime.InteropServices;
// Build Number // Build Number
// Revision // Revision
// //
[assembly: AssemblyVersion("1.4.0")] [assembly: AssemblyVersion("1.5.0")]

7
Source/ViewModels/IMultiPageViewModel.cs
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@ -24,8 +24,11 @@ using Nuclex.Avalonia.Commands;
namespace Nuclex.Avalonia.ViewModels { namespace Nuclex.Avalonia.ViewModels {
/// <summary>Interface for view models that can switch between different pages</summary> /// <summary>Interface for view models that can switch between different pages</summary>
/// <typeparam name="TPageEnumeration">Enum type by which pages can be indicated</typeparam> /// <typeparam name="TPageEnumeration">
public interface IMultiPageViewModel<TPageEnumeration> { /// Type by which pages can be indicated (typically an enum)
/// </typeparam>
public interface IMultiPageViewModel<TPageEnumeration>
where TPageEnumeration : struct {
/// <summary>Command to switch the active tool page</summary> /// <summary>Command to switch the active tool page</summary>
IAsyncCommand<TPageEnumeration> SwitchPageCommand { get; } IAsyncCommand<TPageEnumeration> SwitchPageCommand { get; }

16
Source/ViewModels/MultiPageViewModel.cs
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@ -18,6 +18,7 @@ limitations under the License.
#endregion // Apache License 2.0 #endregion // Apache License 2.0
using System; using System;
using System.Collections;
using System.Collections.Concurrent; using System.Collections.Concurrent;
using System.Threading.Tasks; using System.Threading.Tasks;
@ -27,9 +28,12 @@ using Nuclex.Support;
namespace Nuclex.Avalonia.ViewModels { namespace Nuclex.Avalonia.ViewModels {
/// <summary>Base class for view models that have multiple child view models</summary> /// <summary>Base class for view models that have multiple child view models</summary>
/// <typeparam name="TPageEnumeration">Enum type by which pages can be indicated</typeparam> /// <typeparam name="TPageEnumeration">
/// Type by which pages can be indicated (typically an enum)
/// </typeparam>
public abstract class MultiPageViewModel<TPageEnumeration> : public abstract class MultiPageViewModel<TPageEnumeration> :
Observable, IMultiPageViewModel<TPageEnumeration>, IDisposable { Observable, IMultiPageViewModel<TPageEnumeration>, IDisposable
where TPageEnumeration : struct {
/// <summary>Initializes a new multi-page view model</summary> /// <summary>Initializes a new multi-page view model</summary>
/// <param name="windowManager"> /// <param name="windowManager">
@ -98,8 +102,8 @@ namespace Nuclex.Avalonia.ViewModels {
/// <summary>Switches to another page</summary> /// <summary>Switches to another page</summary>
/// <param name="newPage">New page to switch to</param> /// <param name="newPage">New page to switch to</param>
/// <returns>A task that will finish when the new page has been switched to</returns> /// <returns>A task that will finish when the new page has been switched to</returns>
private Task switchPageAsync(TPageEnumeration? newPage) { private Task switchPageAsync(TPageEnumeration newPage) {
if(newPage.Equals(this.activePage)) { if(Comparer.Default.Compare(this.activePage, newPage) == 0) {
return Task.CompletedTask; return Task.CompletedTask;
} }
@ -116,7 +120,7 @@ namespace Nuclex.Avalonia.ViewModels {
// Double-checked locking to avoid creating a view model for the same page // Double-checked locking to avoid creating a view model for the same page
// multiple times if the construction takes time // multiple times if the construction takes time
object newPageViewModel; object? newPageViewModel;
if(!this.cachedViewModels.TryGetValue(newPage, out newPageViewModel)) { if(!this.cachedViewModels.TryGetValue(newPage, out newPageViewModel)) {
lock(this.cachedViewModels) { lock(this.cachedViewModels) {
if(!this.cachedViewModels.TryGetValue(newPage, out newPageViewModel)) { if(!this.cachedViewModels.TryGetValue(newPage, out newPageViewModel)) {
@ -155,7 +159,7 @@ namespace Nuclex.Avalonia.ViewModels {
private readonly ConcurrentDictionary<TPageEnumeration, object>? cachedViewModels; private readonly ConcurrentDictionary<TPageEnumeration, object>? cachedViewModels;
/// <summary>Page that is currently active in the multi-page view model</summary> /// <summary>Page that is currently active in the multi-page view model</summary>
private TPageEnumeration activePage; private TPageEnumeration? activePage;
/// <summary>View model for the active page</summary> /// <summary>View model for the active page</summary>
private object? activePageViewModel; private object? activePageViewModel;