如何从发件人的子级获取值?
Canvas
上的MouseUp
会创建一个Grid
。
private void ScrollViewer_MouseUp(object sender, MouseButtonEventArgs e)
{
Grid grid = new Grid();
Label timeLabel = new Label();
timeLabel.Content = "06:00"; //this could be anything
timeLabel.Name = "TimeStart"
grid.Children.Add(timeLabel);
canvas.Children.Add(grid);
grid.MouseDown += new MouseButtonEventHandler(ClickEvent);
}
当用户单击已经存在的Grid
时,我希望出现包含timeLabel.Content
的MessageBox
,在本例中为"06:00"
这是行不通的(我也尝试了其他一些,相同的结果)
void ClickEvent(object sender, RoutedEventArgs e)
{
Grid test = (Grid)sender;
Label label = (Label)test.FindName("TimeStart");
MessageBox.Show(label.Content.ToString());
}
错误
An unhandled exception of type 'System.NullReferenceException' occurred in MissionControl M.exe
Additional information: Object reference not set to an instance of an object.
您可以将 Registername
用于标签控件并命名,然后使用 FindName 访问它
private void ScrollViewer_MouseUp(object sender, MouseButtonEventArgs e)
{
NameScope.SetNameScope(grid, new NameScope());
Label timeLabel = new Label();
timeLabel.Name = "label1";
grid.RegisterName("label1", timeLabel);
timeLabel.Content = "06:00";
}
void ClickEvent(object sender, RoutedEventArgs e)
{
Grid test = (Grid)sender;
if (test != null)
{
Label label = (Label)test.FindName("label1");
MessageBox.Show(label.Content.ToString());
}
}
您为网格命名,但您尝试按名称查找标签。选择一个或另一个。也许,命名标签而不是网格最有意义。
你应该命名为标签,然后命名为FindName
或者你可以使用然后第一个网格子:
Grid test = (Grid)sender;
if(test != null)
{
Label label = test.Children[0] as Lable;
MessageBox.Show(label.Content.ToString());
}