0.说明

CommunityToolkit.Mvvm8.1有一个重大更新的功能:源生成器功能,它极大简化我们的mvvm代码

但是本篇先总结一下原写法,下篇再总结源生成器功能

 

1.模型定义

必须继承:ObservableObject

2.viewmodel代码实现

几个关键点:

SetProperty是给属性赋值,并且通知更改通知
ButtonClickCommand.NotifyCanExecuteChanged(); //通知命令 已经改变
RelayCommand ButtonClickCommand //定义命令

	namespace WpfDemoNet6.Demo
	{
	public class DataViewModel1 : ObservableObject
	{
	private string title = "hello";
	public string Title
	{
	get
	{
	return title;
	}
	set
	{
	//title = value;
	//PropertyChanged?.Invoke( this , new PropertyChangedEventArgs( "Name" ) );
	//SetProperty 相当与设置值,并且PropertyChanged通知调用
	SetProperty( ref title , value );
	}
	}
	private bool isEnabled = false;
	/// <summary>
	/// 是否可以使用
	/// </summary>
	public bool IsEnabled
	{
	get => isEnabled;
	set
	{
	SetProperty( ref isEnabled , value );
	//通知命令 已经改变
	ButtonClickCommand.NotifyCanExecuteChanged();
	}
	}
	/// <summary>
	/// 命令
	/// </summary>
	public RelayCommand ButtonClickCommand
	{
	get;
	}
	public DataViewModel1 ()
	{
	//RelayCommand的第一个参数是命令调用语句
	// 第2个参数(可选)是否允许使用
	ButtonClickCommand = new RelayCommand( () =>
	{
	//点击按钮,修改标题
	Title = "hello(改)";
	} , () =>
	{
	return IsEnabled;
	} );
	ButtonClickCommandPar = new RelayCommand<double>( ( double val ) =>
	{
	Title = $"hello(改):{val}";
	} );
	}
	public RelayCommand<double> ButtonClickCommandPar
	{
	get;
	}
	}
	}

3.异步命令

异步命令会自动控制控件的可见性,并且提供一个IsRunning属性可以判断异步是否完成

	public DataViewModel1 ()
	{
	AsyncButtonClickCommand = new AsyncRelayCommand( RunTxtAsync );
	AsyncButtonParClickCommand = new AsyncRelayCommand<double>( RunTxtParAsync );
	}
	/*
	特别说明：异步命令会自动控制控件的可见性,并且提供一个IsRunning属性可以判断异步是否完成
	*/
	/// <summary>
	/// 命令
	/// </summary>
	public IAsyncRelayCommand AsyncButtonClickCommand
	{
	get;
	}
	private async Task RunTxtAsync ()
	{
	await Task.Delay( 4800 );
	Title = "hello(Task改)";
	}
	/// <summary>
	/// 命令(带参数的)
	/// </summary>
	public IAsyncRelayCommand<double> AsyncButtonParClickCommand
	{
	get;
	}
	private async Task RunTxtParAsync ( double val )
	{
	await Task.Delay( 4800 );
	Title = $"hello(Task改):{val}";
	}

	<!--
	特别说明：异步命令会自动控制控件的可见性,并且提供一个IsRunning属性可以判断异步是否完成
	-->
	<Button Width="100"
	Height="30"
	Command="{Binding AsyncButtonClickCommand}"
	Content="异步" />
	<TextBlock HorizontalAlignment="Center"
	FontSize="20"
	FontStyle="Italic"
	FontWeight="Bold"
	Foreground="Green"
	Text="loading......"
	Visibility="{Binding AsyncButtonClickCommand.IsRunning, Converter={StaticResource myboolconvert}}" />