Question

我的应用程序中有一个自定义数据网格，当它的源为空时，它应显示一条消息“无结果”，当源不为空时，它应显示源数据，不应显示任何消息。

我的自定义数据网格是：

namespace GenericControls
{
    [TemplatePart(Name = "EmptyDataGridTextBlock", Type = typeof(TextBlock))]
    public class CustomDataGrid : DataGrid
    {
        private TextBlock _txtEmptyDataGrid = null;

        public static readonly DependencyProperty IsEmptyDataGridProperty = DependencyProperty.Register("IsEmptyDataGrid", typeof(bool), typeof(CustomDataGrid), null);
        public static readonly DependencyProperty EmptyDataGridTextProperty = DependencyProperty.Register("EmptyDataGridText", typeof(string), typeof(CustomDataGrid), null);

        public CustomDataGrid()
        {
            IsEmptyDataGrid = true;
        }

        public bool IsEmptyDataGrid
        {
            get
            {
                return (bool)base.GetValue(IsEmptyDataGridProperty);
            }
            set
            {
                base.SetValue(IsEmptyDataGridProperty, value);
                if(_txtEmptyDataGrid != null)
                {
                    _txtEmptyDataGrid.Visibility = IsEmptyDataGrid ? Visibility.Visible : Visibility.Collapsed;
                }                
            }
        }

        public string EmptyDataGridText
        {
            get
            {
                if (_txtEmptyDataGrid != null)
                {
                    return _txtEmptyDataGrid.Text;
                }

                return (string)base.GetValue(EmptyDataGridTextProperty);
            }
            set
            {
                if (_txtEmptyDataGrid != null)
                {
                    _txtEmptyDataGrid.Text = value;
                }
                base.SetValue(EmptyDataGridTextProperty, value);                
            }
        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            _txtEmptyDataGrid = GetTemplateChild("EmptyDataGridTextBlock") as TextBlock;
            if (_txtEmptyDataGrid != null)
            {
                _txtEmptyDataGrid.Text = EmptyDataGridText;
                _txtEmptyDataGrid.Visibility = IsEmptyDataGrid ? Visibility.Visible : Visibility.Collapsed;
            }
        }
    }
}

我的XAML如下：my：CustomDataGrid Height =“180”Name =“dgChildren”SelectedItem =“{Binding SelectedChild，Mode = TwoWay}”ItemsSource =“{Binding Childrens}” IsEmptyDataGrid =“{Binding IsEmptyDataGrid}“＆GT;

在我的ViewModel中，我有属性IsEmptyDataGrid：

public bool IsEmptyDataGrid
{
    get
    {
        return _isEmptyDataGrid;
    }
    set
    {
        _isEmptyDataGrid = value;
        RaisePropertyChanged("IsEmptyDataGrid");
    }
}

我的问题是，即使我的视图模型中的RaisePropertyChanged("IsEmptyDataGrid")被命中，它也不会进入自定义数据网格中的IsEmptyDataGrid属性，并且空信息会随着数据一起显示在源。

我做错了什么？

提前谢谢你， Kruvi

Answer 1

在这种情况下，并不总是调用DependencyProperty的setter。改为使用回调函数：

public static readonly DependencyProperty IsEmptyDataGridProperty = DependencyProperty.Register("IsEmptyDataGrid", typeof(bool), typeof(CustomDataGrid), new UIPropertyMetaData(false,Callback));

private static void Callback(DependecyObject d, DependencyPropertyChangedEventArgs e)
{
    CustomDatagrid cdt = d as CustomDatagrid;
    if(cdt._txtEmptyDataGrid != null)
        {
            cdt._txtEmptyDataGrid.Visibility = cdt.IsEmptyDataGrid ? Visibility.Visible : Visibility.Collapsed;
        }  
}

MVVM RaisePropertyChanged

1 个答案: