Is there a way to hide the Silverlight grid when running?

LayoutRoot.RowDefinitions[0].Height = new GridLength(0);

Does anyone know how to hide grid rows at runtime?

You cannot set its visibility, the only way is to set its height to 0. Suppose the name of the grid is LayoutRoot and you want to hide the first row:

LayoutRoot.RowDefinitions[0].Height = new GridLength(0);