VisualTreeHelper works only in certain click events and... RSS

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  rajkra

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  35 Points

  41 Posts

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  VisualTreeHelper works only in certain click events and not in page load.

  Aug 12, 2009 05:03 AM | LINK

  Here, I have an expander control in which I have header template.  I am trying to find the textblock inside the header template of the expander control from code behind.  so, I am using this piece of code  which will return the value for count as 1 during click event of certain buttons, but I want to access it in page load itself.  Anyways to do it?

   

   click().....In click event
  

  {
  

   TextBlock tb = GetTextBlockWithParent(this.Expander2, typeof(TextBlock), "tblCurrentBalanceValue");
              tb.UpdateLayout();
              if (tb != null)
              {
                  tb.Text = "583";
              } 
  

   }

   

       public TextBlock GetTextBlockWithParent(UIElement parent, Type targetType, string TextBlockName)
          {
              if (parent.GetType() == targetType && ((TextBlock)parent).Name == TextBlockName)
              {
                  return (TextBlock)parent;
              }
              TextBlock result = null;
              int count = VisualTreeHelper.GetChildrenCount(parent);
              for (int i = 0; i < count; i++)
              {
                  UIElement child = (UIElement)VisualTreeHelper.GetChild(parent, i);
  
                  if (GetTextBlockWithParent(child, targetType, TextBlockName) != null)
                  {
                      result = GetTextBlockWithParent(child, targetType, TextBlockName);
                      break;
                  }
              }
              return result;
          }

   

  This is the definition of it. 

   

   

   

  Raja
• 

  lingbing

  Contributor

  2249 Points

  406 Posts

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  Re: VisualTreeHelper works only in certain click events and not in page load.

  Aug 12, 2009 05:42 AM | LINK

  Hi, this is the control life-cycle issue, in Loaded event, the layout is not updated completedly, so please add your code into the handler of LayoutUpdated event, or if you use Silverlight 3, use the extension method InvokeOnLayoutUpdated, the you can get your code working.

  Regards!

  Ling Bing
  Bei Jing University of Aeronautics and Astronautics
  Bei Jing, China