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}}" />