Thank you for contacting us.
In the current version of the controls the correct enumeration that you have to use is in the Telerik.UI.Xaml.Controls.Grid namespace. To avoid ambiguity, you have to add the whole namespace before the name of the enumeration. We will fix this for the next release. I have updated your telerik points as a token of gratitude for bringing this issue to our attention.
Please, let us if you have further questions.