Why isn't this data binding working?

Why isn't this data binding working?

So I'm brand new to WPF data binding, and it is.. complicated. At this
point, I'm trying to just create a list of premade test items and have it
displayed in a listbox with a data template when I press a button. After
hours of puzzling through tutorials and MSDN this is the best I could come
up with.
The data item I want to make a list from:
class ListingItem
{
private string title;
private string user;
private string category;
//Dummy constructor for test purposes
public ListingItem()
{
title = "TestTitle";
user = "TestUser";
category = "TestCatagory";
}
}
The quick and dirty list creator:
class ListMaker
{
public static List<ListingItem> getListing()
{
List<ListingItem> listing = new List<ListingItem>();
for(int i = 0; i <100; i++)
{
listing.Add(new ListingItem());
}
return listing;
}
}
The XAML of the list itself:
<ListBox x:Name="Listing">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Vertical">
<StackPanel Orientation="Horizontal">
<TextBlock Foreground="Gray" Margin="25,0,0,0"
Text="{Binding user}"/>
<TextBlock Foreground="Gray" Margin="25,0,0,0"
Text="{Binding category}"/>
</StackPanel>
<TextBlock Foreground="Black" Width="270" TextWrapping="Wrap"
Text="{Binding title}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
And finally, the button click event which is SUPPOSED to make the magic
happen:
private void TabClickEvent(object sender, RoutedEventArgs e)
{
Listing.DataContext = RedditScanner.getListing();
}
Problem is, obviously, the magic is not happening. No errors or anything
so easy, I just press that button and dont see any change to the list box.
Any help with this?