How to get screen size and use as resources - WP8

Question

I'm create an app using a LongListSelector with layout grid, I want to get only 3 items per row but the "gridcellsize" property is fixed in WP8, so I think I've to get the device screen size set 1/3 for each item, something like this:

<phone:LongListSelector ItemTemplate="{...}" LayoutMode="Grid" 
        GridCellSize="{StaticResource val},{StaticResource val}"/>

I wrote this in app.xaml.cs but I don't know how to make this to resources

Double val = (Application.Current.RootVisual.RenderSize.Width)/3;

Answer 1

In your App.xaml.xs you just do

double yourWidth = (Application.Current.RootVisual.RenderSize.Width)/3;
double yourHeight = //whatever you want your height to be
Resources.Add("ScreenWidth", yourWidth);
Resources.Add("ScreenHeight", yourHeight);

Then in your xaml you do:

{StaticResource ScreenWidth}

and

{StaticResource ScreenHeight}