wpf - 如何简化 WPF/MVVM 的 ViewModels 中命令的实现？

Question

我注意到，在 MVVM-WPF 场景的 ViewModel 上实现命令时，我重复了很多代码。如下所示，标准实现包括类型为 ICommand 的公共(public)只读字段、私有(private) DelegateCommand 字段和用于执行逻辑的方法。 DelegateCommand 在 ICommand 的 get-accessor 中初始化。

考虑到每个命令的重复，如何才能压缩这种方法？

private DelegateCommand saveCommand;
private DelegateCommand commandClearInputFileList;
private DelegateCommand commandInputFilesDeleteSelected;

public ICommand SaveCommand {
    get {
        if (saveCommand == null) {
            saveCommand = new DelegateCommand(CommitDataBasePush);
        }
        return saveCommand;
    }
}

public ICommand CommandClearInputFileList {
    get {
        if (commandClearInputFileList == null) {
            commandClearInputFileList = new DelegateCommand(InputFilesClear);
        }
        return commandClearInputFileList;
    }
}

public ICommand CommandInputFilesDeleteSelected {
    get {
        if (commandInputFilesDeleteSelected == null) {
            commandInputFilesDeleteSelected = new DelegateCommand(InputFilesDeleteSelected);
        }
        return commandInputFilesDeleteSelected;
    }
}

Answer 1

除了空合并运算符，您还可以使用 Lazy Loading :

private Lazy<DelegateCommand> _cmd = new Lazy<DelegateCommand>(() => new DelegateCommand(InputFilesClear) );

public ICommand CommandClearInputFileList { get { return _cmd.Value; } }

就个人而言，我已经放弃了命令，转而使用 Caliburn.Micro 提供的约定。框架。上面的命令将简单地替换为公共(public)方法。