Question

我是C＃新手，我正在尝试制作一个有两个按钮和一个标签的简单程序。按钮是＆＃34; up＆＃34;和＆＃34; down＆＃34;，标签中的数字会根据它们而变化。当我执行程序时，label显示在viewmodel中定义的初始值。但是当我按下按钮时，它不会更新值。发生更新时，我无法确定哪些不起作用，按钮或标签。谢谢你的时间。

我认为问题在于使用＆＃34; RaisePropertyChanged＆＃34;。我不知道应该怎么用它。如果有人解释，那就好了。

视图中的按钮和标签：

<Button x:Name="Up" Content="Up" HorizontalAlignment="Left" Grid.Row="6" Grid.Column="1"                    VerticalAlignment="Top" Width="75" Grid.ColumnSpan="2" Command="{Binding UpCommand}"/>
<Button x:Name="Down" Content="Down" Grid.Column="3" HorizontalAlignment="Left" Grid.Row="6" VerticalAlignment="Top" Width="75"  Command="{Binding DownCommand}" />
<Label x:Name="Number" HorizontalAlignment="Left" Height="31" Grid.Row="4" VerticalAlignment="Top" Width="161" Content="{Binding Path=Lol, UpdateSourceTrigger=PropertyChanged}" Background="#FFB95151" Grid.ColumnSpan="3" Grid.Column="1"  />

这是ViewModel：

class MainViewModel : BaseINPC
{
    //Number class to hold the number
   private Number lol; //I'm not good at naming
   public Number Lol
   {
       get
       {
           return lol;
       }
       set
       {
           lol = value;
           RaisePropertyChanged("Lol");
       }
   }


    public MainViewModel()
    {
        lol = new Number { number = 5 }; //initial value
        RaisePropertyChanged("Lol");
    }

    #region Commands
    //Up botton commands
    void UpNumber()
    {
        lol.change(true); //it adds 1 to number when True, substracts 1 when false
        RaisePropertyChanged("Lol");
    }

    bool CanUpNumber()
    {
        return true;
    }

    public DelegateCommand UpCommand { get { return new DelegateCommand(UpNumber, CanUpNumber); }                }
    //Down button
    void DownNumber()
    {
        lol.change(false);
        RaisePropertyChanged("Lol");
    }

    bool CanDownNumber()
    {
        return true;
    }

    public DelegateCommand DownCommand { get { return new DelegateCommand(DownNumber, CanDownNumber); } }


    #endregion
  }

这是在我的模型中：

 class Number : INotifyPropertyChanged
{
    private int _number;

    public int number
    {
        get { return _number; }
        set
        {
            _number = value;
        }
    }


    protected void RaisePropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public void change(bool up)
    {
        if (up)
            _number++;
        else
            _number--;

    }


    public override String ToString()
    {
        return "" + _number;
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    #endregion


}

Answer 1

中的

public void change(bool up)
{
    if (up)
        _number++;
    else
        _number--;
    RaisePropertyChanged("number");
}

或

public int number
{
    get { return _number; }
    set
    {
        _number = value;
        RaisePropertyChanged("number");
    }
}

public void change(bool up)
{
    if (up)
        number++;
    else
        number--;
}

您缺少号码属性的通知

还将Label的内容绑定更改为Content="{Binding Path=Lol.number}"，因为number是执行方法change（）时实际更改的属性。

如果在运行时没有更改，可能不需要通知Lol，UpdateSourceTrigger = PropertyChanged与绑定到标签无关，所以也许删除它。

按下按钮时计数的标签在MVVM模式之后的WPF中不起作用

1 个答案: