1. https://www.cnblogs.com/aierong/p/17300066.html
2. https://github.com/aierong/WpfDemo (自我Demo地址)

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}}" />