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MVVM

This document discusses the Model-View-ViewModel (MVVM) pattern. MVVM is a software architectural pattern that separates a software application into three main logical components: the model, the view, and the view model. The model manages the behavior and data of the application domain. The view displays the user interface and processes user input. The view model acts as an intermediary between the model and view by preparing and transferring data between them. MVVM promotes loose coupling between these components. It improves testability and reusability of code. Data binding and notifying property changes are key techniques used in MVVM to synchronize the view model and view. Commanding is used to handle

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314 views27 pages

MVVM

This document discusses the Model-View-ViewModel (MVVM) pattern. MVVM is a software architectural pattern that separates a software application into three main logical components: the model, the view, and the view model. The model manages the behavior and data of the application domain. The view displays the user interface and processes user input. The view model acts as an intermediary between the model and view by preparing and transferring data between them. MVVM promotes loose coupling between these components. It improves testability and reusability of code. Data binding and notifying property changes are key techniques used in MVVM to synchronize the view model and view. Commanding is used to handle

Uploaded by

Kumar Anupam
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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MVVM

Introduction
Jan Schweda
Development Trainer

@ppedv AG C#, WCF, WPF, Azure jan@familieschweda.de http://blog.ppedv.de/author/ JanS.aspx

Agenda
1. Overview
2. Preconditions 3. Model

4. ViewModel
5. View 6. Lets morph our application

OVERVIEW

MVVM Generals
Presented in 2005
Supported UI technologies WPF Silverlight Windows 8 More then 20 frameworks listed on wikipedia

MVVM Structure

View
Presentation Layer

ViewModel
Business Layer

Model

MVVM Benefits
Separation of Concerns
Better Testability More reusable Code

MVVM Elements

HOW DOES IT WORK

DataBinding

Binding Binding Target Binding Source

INotifyPropertyChanged
public interface INotifyPropertyChanged { event PropertyChangedEventHandler PropertyChanged; }
void XXX_PropertyChanged(object sender, PropertyChangedEventArgs e) { // e.PropertyName; }

Commanding
Event Handling

Button Click

Window.xaml

Window.cs

Model

Commanding

Button Click

View.xaml

View.cs

Model

ButtonBase
public abstract class ButtonBase : ContentControl { public ICommand Command { get; set; } public object CommandParameter { get; set; } }

ICommand
public interface ICommand { event EventHandler CanExecuteChanged; bool CanExecute(object parameter); void Execute(object parameter); }

Using Commanding
<Window.CommandBindings> <CommandBinding Command="Close Executed="CommandBinding_Executed CanExecute="CommandBinding_CanExecute"/> </Window.CommandBindings> <Button Command="Close">Klick mich</Button>
private void CB_Executed(object sender, ExecutedRoutedEventArgs e) { // execute here } private void CB_CanExecute(object sender, CanExecuteRoutedEventArgs e) { e.CanExecute = true; }

InvokeCommandAction Behavior
Command functionality for non ButtonBase based

controls Located in System.Windows.Interactivity.dll


<Window xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"> <i:Interaction.Triggers> <i:EventTrigger EventName="Loaded"> <i:InvokeCommandAction Command="Close"/> </i:EventTrigger> </i:Interaction.Triggers> </Window>

MODEL

Model
Dont change if you dont need to

VIEWMODEL

ViewModel Class
Implement INotifyPropertyChanged
Create Property for Model Create Additional Properties

VIEW

What to avoid in the View


Dont use Name or x:Name
Dont use Eventhandler

Decide between IValueConverter and additional

Properties

Connecting ViewModel and View


Bind ViewModel to a View Declaratively in XAML In Code behind Using advanced approaches

Binding the ViewModel declaratively


<Window x:Class="MvvmSample.MainWindow"
xmlns=http://schemas.microsoft.com/winfx/2006/xaml/presentation xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:vm="clr-namespace:MvvmSample.ViewModels"> <Window.Resources> <vm:MainViewModel x:Key="vm"/>

</Window.Resources>
<Grid DataContext="{Binding Source={StaticResource vm}}"> ...

</Grid>
</Window>

Binding the ViewModel in Code


void MainPage_Loaded(object sender, RoutedEventArgs e) { MainPageViewModel vm = new MainPageViewModel(); this.DataContext = vm; }

Questions

Lets transform an application

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