101 lines
5.4 KiB
Markdown
101 lines
5.4 KiB
Markdown
---
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source_files:
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- DTS Viewer/DTS.Viewer/View/Navigation/ViewModel/NavigationViewModel.cs
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generated_at: "2026-04-16T14:03:49.797600+00:00"
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model: "zai-org/GLM-5-FP8"
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schema_version: 1
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sha256: "a00beb6f74b53389"
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---
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# Documentation: NavigationViewModel
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## 1. Purpose
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`NavigationViewModel` is a Prism-based ViewModel responsible for managing the navigation region within the DTS Viewer application's shell. It serves as a mediator between the `INavigationView` and the application's navigation infrastructure, handling notification popups via `InteractionRequest` and providing a bindable `ContextNavigationRegion` property for dynamic content injection. The class inherits from `BaseViewModel<INavigationViewModel>` and implements `INavigationViewModel`.
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---
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## 2. Public Interface
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### Constructor
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```csharp
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public NavigationViewModel(
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INavigationView view,
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IRegionManager regionManager,
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IEventAggregator eventAggregator,
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IUnityContainer unityContainer)
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```
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Initializes the ViewModel, sets the view's `DataContext` to itself, creates `NotificationRequest` and `ConfirmationRequest` instances, and subscribes to the `RaiseNotification` event via the `EventAggregator`.
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### Properties
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| Property | Type | Access | Description |
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|----------|------|--------|-------------|
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| `NavigationView` | `INavigationView` | `get` | Stores the associated view instance. |
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| `NotificationRequest` | `InteractionRequest<Notification>` | `get` | Used to raise notification dialogs. |
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| `ConfirmationRequest` | `InteractionRequest<Confirmation>` | `get` | Used to raise confirmation dialogs. |
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| `ContextNavigationRegion` | `object` | `get/set` | Gets or sets the content of the `NavigationRegion` on the view. Raises `OnPropertyChanged` on set. |
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| `HeaderInfo` | `string` | `get` | Returns the constant string `"NavigationRegion"`. |
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| `IsBusy` | `bool` | `get/set` | **Throws `NotImplementedException`**. |
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| `IsDirty` | `bool` | `get` | **Throws `NotImplementedException`**. |
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### Methods
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| Method | Return Type | Description |
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|--------|-------------|-------------|
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| `Initialize()` | `void` | Override. Empty implementation. |
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| `Initialize(object parameter)` | `void` | Override. Casts `parameter` to `IShellViewModel` and assigns to `Parent` field. |
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| `Activated()` | `void` | Override. **Throws `NotImplementedException`**. |
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| `Cleanup()` | `void` | Override. **Throws `NotImplementedException`**. |
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| `CleanupAsync()` | `Task` | **Throws `NotImplementedException`**. |
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| `InitializeAsync()` | `Task` | Override. **Throws `NotImplementedException`**. |
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| `InitializeAsync(object parameter)` | `Task` | Override. **Throws `NotImplementedException`**. |
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### Events
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| Event | Type | Description |
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|-------|------|-------------|
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| `PropertyChanged` | `PropertyChangedEventHandler` | Declared with `new` keyword, hiding the base implementation. Raised via `OnPropertyChanged`. |
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---
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## 3. Invariants
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- `NavigationView` is set once in the constructor and never reassigned.
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- `ContextNavigationRegion` always accesses `((NavigationView)NavigationView).NavigationRegion.Content`, requiring the concrete `NavigationView` type.
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- `HeaderInfo` always returns the literal string `"NavigationRegion"`.
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- The `RaiseNotification` event subscription is established at construction time and never unsubscribed.
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- `Parent` is only set via `Initialize(object parameter)` and expects an `IShellViewModel` instance.
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---
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## 4. Dependencies
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### This module depends on:
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- `DTS.Common.Base` — `BaseViewModel<T>`
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- `DTS.Common.Events` — `RaiseNotification` event, `NotificationContentEventArgs`, `NotificationContentEventArgsWithoutTitle` (implied by usage)
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- `DTS.Common.Interface` — `INavigationViewModel`, `INavigationView`, `IShellViewModel`
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- `Microsoft.Practices.Prism.Events` — `IEventAggregator`
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- `Microsoft.Practices.Prism.Interactivity.InteractionRequest` — `InteractionRequest<T>`, `Notification`, `Confirmation`
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- `Microsoft.Practices.Prism.Regions` — `IRegionManager`
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- `Microsoft.Practices.Unity` — `IUnityContainer`
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### What depends on this module:
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- **Unclear from source alone** — The `IShellViewModel` interface suggests a parent shell consumes this ViewModel, but the exact consumers are not visible in this file.
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---
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## 5. Gotchas
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1. **Many members throw `NotImplementedException`**: `IsBusy`, `IsDirty`, `Activated()`, `Cleanup()`, `CleanupAsync()`, `InitializeAsync()`, and `InitializeAsync(object parameter)` are all stubs that will crash if invoked. This indicates incomplete implementation.
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2. **Broken abstraction in `ContextNavigationRegion`**: The property casts `INavigationView` to the concrete `NavigationView` type to access `NavigationRegion.Content`. This violates the interface contract and creates tight coupling.
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3. **Incorrect XML documentation**: The constructor's XML comment states it "Creates a new instance of the TechnologyDoFrontEditViewModel" — this is a copy-paste error and does not match the actual class name.
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4. **Event hiding**: The `PropertyChanged` event and `OnPropertyChanged` method are declared with `new`, hiding the base class implementation. This could lead to unexpected behavior if consumers expect the base event to fire.
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5. **No event unsubscription**: The `RaiseNotification` event subscription in the constructor has no corresponding unsubscription in `Cleanup()` (which throws anyway), potentially causing memory leaks.
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6. **Commented-out dead code**: A `GetRegions()` method is entirely commented out, suggesting unfinished or abandoned functionality. |