MVVM Pattern for .NET

Trigger On

• implementing UI separation with Model-View-ViewModel
• using MVVM Toolkit (CommunityToolkit.Mvvm) for ViewModels
• designing testable UI architecture
• handling commands, property changes, and messaging
• choosing between MVVM frameworks

Workflow

1. Keep Views dumb — no business logic in code-behind
2. Use data binding — connect View to ViewModel properties
3. Commands for actions — handle user interactions via ICommand
4. Inject dependencies — services go into ViewModel constructors
5. Test ViewModels — they should be unit testable without UI

Deliver

• ViewModels that are fully unit testable
• Clean separation between UI and business logic
• Proper use of commands and data binding
• Messaging for loose coupling between components

Validate

• No business logic in code-behind files
• ViewModels don't reference View types
• Commands are used for all user actions
• Properties use ObservableProperty or equivalent
• Dependencies are injected, not created
• Unit tests cover ViewModel logic

References

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