Access Element inside Silverlight DataTemplate

Question

I have not been able to find a clean solution to the following problem even though there are a few related questions already on SO.

If I have a data template that is being used multiple times, for example, a TreeViewItem.HeaderTemplate, how can I change something the template for only some of the TreeViewItems.

For example, let's say my TVI HeaderTemplate has a textblock and depending on the string, I want to make the fontweight bold.

I want to do something like this:

((TextBlock)myTreeView.Items.ElementAt(0).FindName("myTextBlock")).FontWeight = FontWeights.Bold;

Does anyone have a solution for this? --> Thanks Evan

Edit: Is there a way to write a generic function to get a control based on it's name even if it's in a data template?

LayoutRoot.FindName("myTextBlock"); would work if myTextBlock was not in a datatemplate. How can I write a findElementInDataTemplate(string elementName, string parentName) function?

The reason Evan's answer is not what I'm looking for is because I am developing a control. I want the application developer who uses my control to be able to change any element in the control. If I use Evan's solution, that would require the application developer to have access to all the templates in the control. Possible, but not ideal. Thanks!

Answer 1

One way I have accomplished this is to store all the needed items in a class-level collection variable by using the Loaded event of the control. Take this DataTemplate for example.

<DataTemplate>
   ...
   <TextBlock Loaded="TemplateTextBlock_Loaded" />
</DataTemplate>

Then you use the Loaded event to load up some sort of collection for later use.

private List<TextBlock> templateTextBlocks = new List<TextBlock>();

private void TemplateTextBlock_Loaded(object sender, RoutedEventArgs e)
{
   TextBlock tb = sender as TextBlock;
   if (!this.templateTextBlocks.Contains(tb)) this.templateTextBlocks.Add(tb);
}

Of course, if you're going to be loading and unloading the control, this may not work well for you.

Answer 2

If you're using data binding, have you tried using a binding converter? In this case you would do something like...

FontWeight={Binding Path=TextProperty, Converter={StaticResource BoldConverter}}

And the converter would be along the lines of...

string myTestString = (string)value;
if (myTestString.Contains("Bob"))
    return FontWeights.Bold;
return FontWeights.Normal;

Which makes it less painful to try and root through the elements to locate a particular one.