Line numbers in stack traces for UWP apps

I created a blank Universal Windows App project in Visual Studio 2015.

I add something like:

try {
    string foo = null;
    int len = foo.Length;
} catch (Exception ex) {
    System.Diagnostics.Debug.WriteLine(ex);
}

I get a stack trace like:

Exception thrown: 'System.NullReferenceException' in TestStackTraces.exe
System.NullReferenceException: Object reference not set to an instance of an object.
at TestStackTraces.App.OnLaunched(LaunchActivatedEventArgs e)

i.e., No line numbers.

How do I get line numbers to show up?