Net MAUI中[NotifyCanExecuteChangedFor]目标需为可访问IRelayCommand属性报错

问题原因 #

报错的核心是**[NotifyCanExecuteChangedFor]指定的目标名称错误**。当你给带参数的方法标记[RelayCommand]特性时，MVVM Toolkit会自动生成名为[方法名]Command的IRelayCommand属性——比如你的SetBusy方法会生成SetBusyCommand，而你当前写的nameof(SetBusy)指向的是原方法，并非生成的命令属性，所以工具无法识别到合法的IRelayCommand目标。

修正后的代码 #

将[NotifyCanExecuteChangedFor(nameof(SetBusy))]替换为[NotifyCanExecuteChangedFor(nameof(SetBusyCommand))]即可解决问题：

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input; 

namespace uManageMobileApp.ViewModel
{
    public partial class BaseViewModel : ObservableObject
    {
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(SetBusyCommand))]
        public bool isBusy = false;

        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(SetBusyCommand))]
        public string? busyLable = string.Empty;


        [RelayCommand]
        public async void Back()
        {
            await Shell.Current.GoToAsync($"..");
        }

        [RelayCommand]
        public void SetBusy(string busyText)
        {
            this.IsBusy = true;
            this.BusyLable = busyText;
        }

        [RelayCommand]
        public void SetNotBusy()
        {
            this.IsBusy = false;
            this.BusyLable = string.Empty;
        }
    }
}

内容的提问来源于stack exchange，提问作者Taras Lisniak