Hello Marc Roussel,
I don't seem to grasp what the issue is here. From what I gather the sample i have sent you is achieves your requirements. I understand that this might look like quite a bit of XAML but this is to be expected as it is the nature of the platform. Working with styles and templates is the right way to go and therefore if you do it right there should not be any need of writing C# code to achieve styling.
If you take a careful look at the XAML you will see that there really is nothing special about it.
1. The new row height is defined in 3 lines with a style setter.
2. The group row required template editing and TemplateBinding the MinHeight to a couple of elements in order to get it to work. This is now implemented in the grid and will be available with the upcoming Q2.Beta. Bottom line is you will be able to do it the same way as the new row - with 3 lines of XAML.
3. The ScrollBars width and height is achieved via editing the template of the scroll viewer and setting MinWidth and MinHeight to the scrollbars.
The sample was made entirely via the Blend UI though I have to admit there I was looking at the output XAML to save time in preparing it.
The only real issue here is the Exception you are getting in your follow-up post which will look into.
As for the implementation in your project - the styles are implicit so Copy / Pasting them should be sufficient to get you started. You might need to do some namespace tweaking if you are not using the telerik URI namespace, but again that is to be expected when pasting from another person's code.
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