Collection property '__implicit_items' is null when setting transitions in Win Store app

windows-store-apps

Solution

You need to set the collection.

<Grid>
  <Grid.Transitions>
    <TransitionCollection>
      <EntranceThemeTransition FromHorizontalOffset="300" />
    </TransitionCollection>
  </Grid.Transitions>
</Grid>

Remember that XAML is just object-instantiation and property-setting mark-up and the Transitions property on the Grid is a collection and thus needs setting to a collection instance. No idea why it doesn't barf on the invalid type or why Intellisense suggests the bad syntax, but hey ho.

Problem

When trying to set a transition using the Transitions collection on a Panel, like a Grid or something, like so: ``` <Grid> <Grid.Transitions> <EntranceThemeTransition FromHorizontalOffset="300" /> </Grid.Transitions> </Grid> ``` I get the following error at runtime: ``` Collection property '__implicit_items' is null. ```

Original source