How do I make a WPF data template fill the entire width of the listbox?

Question

I have a ListBox DataTemplate in WPF. I want one item to be tight against the left side of the ListBox and another item to be tight ag

Answer 1

If you want to use a Grid, then you need to change your ColumnDefinitions to be:

If you don't need to use a Grid, then you could use a DockPanel:

Notice the TextBlock at the end. Any control with no "DockPanel.Dock" defined will fill the remaining space.