wpf通知更改INotifyPropertyChanged

 按钮更新文本框需要通知事件

<Grid>
        <StackPanel>
            <TextBlock Text="{Binding Name}"></TextBlock>
            <Button Content="Show" Command="{Binding ShowCommand}"></Button>
        </StackPanel>
    </Grid>

using System;
using System.Windows.Input;


namespace wpf命令
{
    public class MyCommand : ICommand
    {
        Action executeAction;
        public MyCommand(Action action)
        {
            executeAction = action;
        }
        //命令状态改变触发
        public event EventHandler? CanExecuteChanged;

        //能不能执行动作
        public bool CanExecute(object? parameter)
        {
            
            return true;
        }

        //执行动作具体代码
        public void Execute (object? parameter)
        {
            executeAction();
        }
    }
}

using System.ComponentModel;
//using System.Runtime.CompilerServices;
using System.Windows;


namespace wpf命令
{
    public class MainViewModel: INotifyPropertyChanged
    {
        //绑定ui
        public MyCommand ShowCommand { get; set; }
        private string name;

//这种写法比较重
        public string Name
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Name"));
            }
        }

        public MainViewModel()
        {
            ShowCommand = new MyCommand(Show);
            Name = "Hello";
        }

        public event PropertyChangedEventHandler PropertyChanged;

        //UI分离
        //跟按钮建立关系
        public void Show()
        {
            Name = "我点击了按钮";
            MessageBox.Show(Name);
        }
    }
}

namespace wpf命令
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            //上下文
            this.DataContext = new MainViewModel();
        }
    }
}

 

 增加一项需要加很多代码

 改进

把通知事件单独写道一个类

using System.ComponentModel;

namespace wpf命令
{
    public class ViewModeBase: INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        //属性通知更改propertyName属性
        public void OnPropertyChanged(string propertyName)
        {
            PropertyChanged?.Invoke (this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

using System.ComponentModel;
//using System.Runtime.CompilerServices;
using System.Windows;


namespace wpf命令
{
    public class MainViewModel: ViewModeBase
    {
        //绑定ui
        public MyCommand ShowCommand { get; set; }
        private string name;
        public string Name
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
                OnPropertyChanged("Name");
            }
        }
        public string title;
        public string Title
        {
            get { return title; }
            set { title = value; OnPropertyChanged("Title"); }
        }

        public MainViewModel()
        {
            ShowCommand = new MyCommand(Show);
            Name = "Hello";
        }

        

        //UI分离
        //跟按钮建立关系
        public void Show()
        {
            Name = "我点击了按钮";
            MessageBox.Show(Name);
        }
    }
}

在改进自动识别传参

using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace wpf命令
{
    public class ViewModeBase: INotifyPropertyChanged
    {
        //没有显示订阅该事件
        //内部实现通知更改
        public event PropertyChangedEventHandler PropertyChanged;
        //属性通知更改propertyName属性
        //特性[CallerMemberName] 调用默认属性
        public void OnPropertyChanged([CallerMemberName] string propertyName = "")
        {
            //按照约定规则Invoke
            PropertyChanged?.Invoke (this, new PropertyChangedEventArgs(propertyName));
        }
    }
}