Grid.Add.Children(UIElement)返回参数不正确的异常

Question

我正在尝试在两个pivot项目中添加边框。

当我的边界第一次被添加到pivot项目的网格中时，一切都很好。但是，当我尝试添加边界第二次在同一枢轴项目它抛出一个异常"参数不正确"下面是我的代码:

private void pivot_item1Loaded()
        {
            WebClient webClient2011 = new WebClient();
            string Url2011 = "http://hostname/Details/Images?year=2011" + "&time=" + System.DateTime.UtcNow;
            webClient2011.OpenReadAsync(new Uri(Url2011));
            webClient2011.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted2011);
        }
        private void pivot_item2Loaded()
        {
            WebClient webClient2012 = new WebClient();
            string Url2012 = "http://hostname/Details/Images?year=2012" +"&time="+ System.DateTime.UtcNow;
            webClient2012.OpenReadAsync(new Uri(Url2012));
            webClient2012.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted2012);
        }
        public void webClient_OpenReadCompleted2011(object sender, OpenReadCompletedEventArgs e)
        {
            StringBuilder output = new StringBuilder();
            try
            {               
                using (XmlReader reader = XmlReader.Create(e.Result))
                {
                    while (reader.Read())
                    {
                        if (reader.NodeType == XmlNodeType.Element)
                        {
                            if (reader.Name == "iconPath")
                            {
                                string iconPath = reader.ReadElementContentAsString();
                                iconImages2011.Add(iconPath);
                            }
                            if (reader.Name == "imagePath")
                            {
                                string imagePath = reader.ReadElementContentAsString();
                                fullScreenImages2011.Add(imagePath);
                            }
                        }
                    }
                }
                int numOfRows = (iconImages2011.Count) / 3 + 1;
                for (int j = 0; j < numOfRows; j++)
                {
                    //pivot_item1 
                    ContentPanel2011.RowDefinitions.Add(new RowDefinition() { Height = new GridLength(150) });
                }
                int rowCount = 0;
                int columnCount = 0;
                for (int i = 0; i < iconImages2011.Count; i++)
                {
                    Border border2011 = new Border();
                    border2011.Background = new SolidColorBrush(Colors.Blue);
                    border2011.Height = 110;
                    border2011.Width = 110;
                    border2011.CornerRadius = new CornerRadius(10);
                    Canvas canvas2011 = new Canvas();
                    canvas2011.Height = 110;
                    canvas2011.Width = 110;
                    BitmapImage AppImage = new BitmapImage(new Uri(iconImages2011[i], UriKind.Absolute));
                    Image img = new Image();
                    img.Source = AppImage;
                    img.Width = 90;
                    img.Height = 90;
                    img.Stretch = Stretch.Fill;
                    img.Margin = new Thickness(10, 10, 10, 10);
                    canvas2011.Children.Add(img);
                    border2011.Child = canvas2011;
                    border2011.Name = i.ToString();
                    Grid.SetColumn(border2011, columnCount);
                    Grid.SetRow(border2011, rowCount);
                    ContentPanel2011.Children.Add(border2011);
                    pivot2011.Content = ContentPanel2011;
                    if (columnCount < 2)
                    {
                        columnCount++;
                    }
                    else if (columnCount == 2)
                    {
                        columnCount = 0;
                        rowCount++;
                    }
                }
            }
            catch (Exception x)
            {
                MessageBox.Show(x.Message);
            }
        }

这段代码第一次工作，但给出了异常之后，ContentPanel2011 viz pivot_item1没有得到填充的border2011

Answer 1

完成。在再次设置内容之前，请先将pivot上的content属性设置为null。

我刚刚添加了:

pivot2011.Content = null;
pivot2012.Content = null;

pivot_item1Loaded()和pivot_item2Loaded()