WPF 异步命令实现

参考

• 豆包

环境

软件/系统	版本	说明
Windows	windows 10 专业版 22H2 64 位操作系统, 基于 x64 的处理器
Microsoft Visual Studio	Community 2022 (64 位) - Current 版本 17.13.6
.NET Framework	4.8

部分代码

1. AsyncRelayCommand.xaml

   using System;
   using System.Collections.Generic;
   using System.Linq;
   using System.Text;
   using System.Threading.Tasks;
   using System.Windows.Input;
   
   namespace WpfApp1
   {
   	public class AsyncRelayCommand : ICommand
   	{
   		private readonly Func<Task> _execute;
   		private readonly Func<bool> _canExecute;
   		private bool _isExecuting;
   
   		public AsyncRelayCommand(Func<Task> execute, Func<bool> canExecute = null)
   		{
   			_execute = execute;
   			_canExecute = canExecute;
   		}
   
   		public event EventHandler CanExecuteChanged
   		{
   			add => CommandManager.RequerySuggested += value;
   			remove => CommandManager.RequerySuggested -= value;
   		}
   
   		public bool CanExecute(object parameter)
   		{
   			return !_isExecuting && (_canExecute?.Invoke() ?? true);
   		}
   
   		public async void Execute(object parameter)
   		{
   			if (CanExecute(parameter))
   			{
   				try
   				{
   					_isExecuting = true;
   					await _execute();
   				}
   				finally
   				{
   					_isExecuting = false;
   				}
   
   				// 触发CanExecuteChanged事件，更新命令状态
   				CommandManager.InvalidateRequerySuggested();
   			}
   		}
   	}    }
   

2. ViewModelBase.cs

   using System;
   using System.Collections.Generic;
   using System.ComponentModel;
   using System.Linq;
   using System.Runtime.CompilerServices;
   using System.Text;
   using System.Threading.Tasks;
   
   namespace WpfApp1
   {
   	public class ViewModelBase : INotifyPropertyChanged
   	{
   		public event PropertyChangedEventHandler PropertyChanged;
   
   		public void OnPropertyChanged([CallerMemberName] string propName = null)
   		{
   			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
   		}
   
   	}
   }
   
   

3. MainWindowVM.cs

   using System;
   using System.Collections.Generic;
   using System.Diagnostics;
   using System.Linq;
   using System.Text;
   using System.Threading.Tasks;
   using System.Windows;
   using System.Windows.Input;
   
   namespace WpfApp1
   {
   	public class MainWindowVM : ViewModelBase
   	{
   
   		// 需要显式设置 get读取器才能在 XAML 中绑定
   		public ICommand MyAsyncCommand { get; }
   
   		public MainWindowVM()
   		{
   			MyAsyncCommand = new AsyncRelayCommand(ExecuteMyAsyncCommand);
   		}
   
   		private async Task ExecuteMyAsyncCommand()
   		{
   			// 执行异步操作
   			await Task.Run(() =>
   			{
   
   				// 模拟耗时操作
   				System.Threading.Thread.Sleep(2000);
   				// 在 UI 线程中更新
   				Application.Current.Dispatcher.Invoke(() =>
   				{
   					MessageBox.Show("12312");
   				});
   				Debug.WriteLine(12312);
   			});
   		}
   	}
   }
   
   

同步命令

1. RelayCommand.cs

   using System;
   using System.Collections.Generic;
   using System.Linq;
   using System.Text;
   using System.Threading.Tasks;
   using System.Windows.Input;
   
   namespace WpfApp1
   {
   	public class RelayCommand : ICommand
   	{
   		private readonly Func<Task> _execute;
   		private readonly Func<bool> _canExecute;
   
   		public RelayCommand(Func<Task> execute, Func<bool> canExecute = null)
   		{
   			_execute = execute ?? throw new ArgumentNullException(nameof(execute));
   			_canExecute = canExecute;
   		}
   
   		public event EventHandler CanExecuteChanged
   		{
   			add => CommandManager.RequerySuggested += value;
   			remove => CommandManager.RequerySuggested -= value;
   		}
   
   		public bool CanExecute(object parameter) => _canExecute?.Invoke() ?? true;
   
   		public async void Execute(object parameter) => await _execute();
   	}
   }