Implementing M-V-VM pattern in WPF

• Model-View-ViewModel is a design pattern used to create client applications that take advantage of data-binding in WPF
• View = Thing you see on the screen that the user interacts with
• View-Model = something that the view binds to/ the visual state of the data
• Model = your data object
• Interaction between the view and the view-model is done by data binding
• Things to know before approaching this pattern:
  • Become familiar with XAML including data-binding and use of commands
• Workflow
  • Consider how the view is going to bind to the View-Model
    • What properties are expected?
  • Create the view and identify the properties required for binding
  • Create the view-model that exposes the properties required by the view
• Building a View-Model
  • Consider building presentation friendly adapter around the model object
  • Think about taking a view and creating a VM that stores the state of the view
  • When you build a VM, pass in the model (data model) to the constructor so that you can easily connect and use the model from within the VM
  • VM is just an adapter or a wrapper class where it is wrapping the original model, wrapping can be done in the constructor or using the lazy load method i.e. on property getters
  • VMs can also be used to wrap other VMs
  • Set the VM as the data context of the view
  • Add state properties to the VM as required
  • Consider defining interface for the VM so that the contract between the View and the VM is well defined
  • Instead of using click handler use command binding. This will make unit testing easier as commands are exposed by the VM. Command in WPF implement ICommand interface
• Files you might end up with:
  • SomeView.xaml
  • ISomeViewModel.cs
  • SomeViewModel.cs
  • ISomeModel.cs
  • SomeModel.cs