C# Delegatecommand、relaycommand 和 routedcommand 的区别
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Difference between Delegatecommand, relaycommand and routedcommand
提问by Zaz
I'm confused about command pattern. There are so many different explanations about the commands. I thought the code below was delegatecommand, but after reading about the relaycommand, I am in doubt.
我对命令模式感到困惑。关于命令有很多不同的解释。我以为下面的代码是delegatecommand，但是在阅读relaycommand 之后，我有疑问。
What is the difference between relaycommand, delegatecommand and routedcommand. Is it possible to show in examples that have relevance to my posted code?
中继命令、委托命令和路由命令之间有什么区别。是否可以在与我发布的代码相关的示例中显示？
class FindProductCommand : ICommand
{
ProductViewModel _avm;
public FindProductCommand(ProductViewModel avm)
{
_avm = avm;
}
public bool CanExecute(object parameter)
{
return _avm.CanFindProduct();
}
public void Execute(object parameter)
{
_avm.FindProduct();
}
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
}
采纳答案by Zev Spitz
Your FindProductCommandclass implements the ICommandinterface, which means it can be used as a WPF command. It is neither a DelegateCommandnor a RelayCommand, nor is it a RoutedCommand, which are other implementations of the ICommandinterface.
您的FindProductCommand类实现了ICommand接口，这意味着它可以用作WPF命令。它既不是 aDelegateCommand也不是 a RelayCommand，也不是 a RoutedCommand，它们是ICommand接口的其他实现。
FindProductCommandvs DelegateCommand/RelayCommand
FindProductCommand对比DelegateCommand/RelayCommand
Generally, when an implementation of ICommandis named DelegateCommandor RelayCommand, the intention is that you don't have to write a class that implements the ICommandinterface; rather, you pass the necessary methods as parameters to the DelegateCommand/ RelayCommandconstructor.
通常，当 的实现ICommand命名为DelegateCommandor 时RelayCommand，目的是您不必编写实现该ICommand接口的类；相反，您将必要的方法作为参数传递给DelegateCommand/RelayCommand构造函数。
For example, instead of your entire class, you could write:
例如，你可以这样写，而不是整个班级：
ProductViewModel _avm;
var FindPoductCommand = new DelegateCommand<object>(
parameter => _avm.FindProduct(),
parameter => _avm.CanFindProduct()
);
(Another, perhaps greater benefit than the savings in boilerplate code -- if you instantiate the DelegateCommand/ RelayCommandwithin your viewmodel, your command has access to the internal state of that viewmodel.)
（另一个可能比节省样板代码更大的好处——如果您在视图模型中实例化DelegateCommand/ RelayCommand，您的命令可以访问该视图模型的内部状态。）
Some implementations of DelegateCommand/ RelayCommand:
DelegateCommand/ 的一些实现RelayCommand：
- Microsoft Prism DelegateCommand reference
- WPF Tutorial implementation of
ICommandcalledDelegateCommand - Another implementationalso called
DelegateCommand - The original implementation of
RelayCommandby Josh Smith
- Microsoft Prism DelegateCommand 参考
ICommand被调用的WPF教程实现DelegateCommand- 另一种实现也称为
DelegateCommand - 由 Josh Smith的原始实现
RelayCommand
Related:
有关的：
FindProductCommandvs RoutedCommand
FindProductCommand对比 RoutedCommand
Your FindProductCommandwill execute FindProductwhen triggered.
您FindProductCommand将FindProduct在触发时执行。
WPF's built-in RoutedCommanddoes something else: it raises a routed eventwhich can be handled by other objects in the visual tree. This means you can attach a command binding to those other objects to execute FindProduct, while attaching the RoutedCommanditself specifically to one or more objects that trigger the command, e.g. a button, a menu item, or a context menu item.
WPF 的内置功能RoutedCommand还有其他功能：它引发一个路由事件，该事件可由可视化树中的其他对象处理。这意味着您可以将命令绑定附加到要执行的其他对象FindProduct，同时将其RoutedCommand本身专门附加到触发命令的一个或多个对象，例如按钮、菜单项或上下文菜单项。
Some related SO answers:
一些相关的SO答案：
