带参数的通用 Windows 平台命令 [英] Universal Windows Platform commanding with parameters

问题描述

如何在没有 MVVM 框架的情况下在通用 Windows 平台中创建参数化命令?我试图实现 RelayCommand 类，但 System.Windows.Input 命名空间没有 CommandManager 类.

How I can make parameterized commands in Universal Windows Platform without MVVM-frameworks? I was tried to implement RelayCommand class, but System.Windows.Input namespace haven't CommandManager class.

推荐答案

如果不想使用框架，则必须自己实现接口System.Windows.Input.ICommand.

If you don't want to use a framework, you have to implement the interface System.Windows.Input.ICommand yourself.

命令参数可以通过属性CommandParameter 传递.不需要命令管理器.如果您对参数使用单向绑定，则当绑定更改时，按钮将自动启用/禁用.对于任何其他引发事件 CanExecuteChanged.

Command parameters can be passed by the the property CommandParameter. There is no need for a command manager. If you use a one-way binding for the parameter, the button will be enabled / disabled automatically when the binding change. For anything else raise the event CanExecuteChanged.

当然，在更高级的场景中，您还必须为命令实现一些状态管理，如果命令在视图模型中定义或使用某种自我实现的命令管理器，这会更容易.

Of course, in a more advanced scenario, you'll have to implement some state management for the command as well, which is easier if the commands are defined in a viewmodel or use are using some kind of self implemented command manager.

简化示例

这里是一个如何使用带有 x:Bind 绑定的按钮的简化示例.不需要视图模型或命令管理器.

Here a simplified example how to use a button with x:Bind binding. No view model or command manager is reuired.

示例.xaml:

<Button x:Name="Test" Command="{x:Bind FirstCommand}" CommandParameter="{x:Bind SelectedItem, Mode=OneWay">
   <TextBlock>Test</TextBlock>
</Button>

示例.xaml.cs:

Example.xaml.cs:

public sealed partial class Example : Page {

    public SampleCommand FirstCommand { get; set; } =
        new SampleCommand();

    public object SelectedItem { get; set; }

    public StandardProjectList() {
        this.InitializeComponent();
    }

}

SampleCommand.cs:

SampleCommand.cs:

public class SampleCommand : ICommand {

    public event EventHandler CanExecuteChanged;

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

    public void Execute(object parameter) {
        if (CanExecute(parameter))
            //...
    }   
}

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