WPF-MVVM计数器

简单的计数案例，ViewModel开启辅助线程，模拟后端运行，该方式可以扩展为项目中的后端线程数采及运算呈现，便于实时监控数据的场景。

代码如下：

MyCommand

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;

namespace MVVMCountDemo.ViewModel
{
    public class MyCommand : ICommand
    {
        private readonly Action _execute;
        private readonly Func<bool> _canExecute;

        public MyCommand(Action execute, Func<bool> canExecute = null)
        {

            _execute = execute;
        }

        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public bool CanExecute(object parameter)
        {
            return _canExecute == null || _canExecute();
        }

        public void Execute(object parameter)
        {
            _execute();
        }



    }
}

Notify  

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace MVVMCountDemo.ViewModel
{
    public abstract class Notify : INotifyPropertyChanged
    {

        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged([CallerMemberName] string name = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
        }

    }
}

Window.xaml

<Window x:Class="MVVMCountDemo.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:MVVMCountDemo"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Label  FontSize="30" Content="{Binding Seconds}"   Foreground="Black" HorizontalAlignment="Left" Margin="141,85,0,0" VerticalAlignment="Top" Height="110" Width="230"/>
        <Button Content="开始/清零" HorizontalAlignment="Left" Margin="203,224,0,0" VerticalAlignment="Top" Width="100" Command="{Binding StartOrResetCommand}"/>
    </Grid>
</Window>

MainWindow.cs

using MVVMCountDemo.ViewModel;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace MVVMCountDemo
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            this.DataContext = new CountDemoViewModel();
        }
    }
}

CountDemoViewModel 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
using System.Windows.Threading;

namespace MVVMCountDemo.ViewModel
{
    public class CountDemoViewModel:Notify
    {

        private DispatcherTimer timer;
        private int seconds = 0;

        public int Seconds
        {
            get { return seconds; }
            set
            {
                if (seconds != value)
                {
                    seconds = value;
                    OnPropertyChanged(nameof(Seconds));
                }
            }
        }


        public ICommand StartOrResetCommand { get; private set; }

        public CountDemoViewModel()
        {
            timer = new DispatcherTimer();
            timer.Interval = TimeSpan.FromSeconds(1);
            timer.Tick += Timer_Tick;
            StartOrResetCommand = new MyCommand(StartOrReset);
        }

        int currentCount = 0;
        int lastCount = 0;

        private void Timer_Tick(object sender, EventArgs e)
        {
            currentCount++;
            Seconds = currentCount - lastCount;
        }




        private void StartOrReset()
        {
            if (timer.IsEnabled)
            {
                timer.Stop();
                Seconds = 0;
                lastCount = currentCount;
            }
            else
            {
                timer.Start();
            }
        }

    }
}