我應該如何使用 Avalonia(ReactiveUI) 控制命令的可執行性？

Question

我正在嘗試根據本指南實現控制 ReactiveUI 命令的可執行性： 指南。
但我遇到了一個例外：“由於 object 的當前 state，操作無效。”
我應該如何解決這個問題？
我的代碼示例：

public class CreateBookViewModel : ViewModelBase
{
    IObservable<bool> canExecuteCreateBookCommand;
    private string? name;
    private string? path;
    public ReactiveCommand<Unit, Unit> ChangePathCommand { get; }
    public ReactiveCommand<Unit, EditBookViewModel?> CreateBookCommand { get; }


    public string? Name 
    {
        get => name;
        set => this.RaiseAndSetIfChanged(ref name, value);
    }
    public string? Path
    {
        get => path;
        set => this.RaiseAndSetIfChanged(ref path, value);
    }

    public CreateBookViewModel()
    {
        canExecuteCreateBookCommand = this.WhenAnyValue(x => x.path, x => x.name, (name, path) =>
            !string.IsNullOrWhiteSpace(name) && !string.IsNullOrWhiteSpace(path));
        ChangePathCommand = ReactiveCommand.CreateFromTask(RunChangePath);
        CreateBookCommand = ReactiveCommand.Create(RunCreateBook, canExecuteCreateBookCommand);
    }

    private async Task RunChangePath()
    {
       var dialog = new OpenFolderDialog();
       Path = await dialog.ShowAsync(CreateBookWindow.Instance);
    }

    private  EditBookViewModel? RunCreateBook()
    {
        if(name!= null && path!= null)
        {
            EditBookViewModel book = new EditBookViewModel(name, path);
            return book;
        }
        return null;
    }

}

Answer 1

在this.WhenAnyValue您的選擇器表達式指向字段而不是屬性。 將其更改為this.WhenAnyValue(x => x.Path, x => x.Name, (name, path) =>.string.IsNullOrWhiteSpace(name) &&;string.IsNullOrWhiteSpace(path)); .