How do you span columns in C#?

How do you span columns in C#?
In silverlight, suppose you have a grid, and this grid is in 3 columns.
and you want to add a UserControl to this grid but you want it to span all three
columns. How would that C# code look like?
Grid1.Children.Add(UserControl01);
But then what?
Grid1.Children.ElementAt(1).SetValue(Grid.SetRowSpan, 2);
??

Grid1.Children.Add(UserControl01);

Grid.SetColumnSpan(UserControl01, 3);