Hi Frank Richardson,
What you describe is a common Silverlight VisualTree problem. It isn't just the Telerik RadGridView control that exhibits this behavior. Pretty much any Silverlight based control that can have lots of data behind it will exhibit this behavior. It's the nature of Microsoft's Silverlight engine and how they choose to render the VisualTree.
Currently the only way to access those other rows you're after is to actually scroll the tree so that they become visible and then read them.
When we can find a better solution, we'll post it in a blog post.
the Telerik team
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