During the migration of WPF projects based on. Net framework to. Net core 3, system.windows.interactivity is no longer compatible.

The following is the specific migration process:

1. Replace package

Open nuget package manager, remove references to Microsoft.Expression.Interactions and System.Windows.Interactivity, and install Microsoft.Xaml.Behaviors.Wpf package.

2. Replace xmlns namespace

Here is an example code:

xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" 
xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions" 

Replaced by:

xmlns:Behaviors="http://schemas.microsoft.com/xaml/behaviors"

3. Replace the namespace in the class file

Microsoft.Xaml.Interactivity and Microsoft.Xaml.Interactions replace by Microsoft.Xaml.Behaviors

More about Microsoft.Xaml.Behaviors.Wpf ，Click XAMLBehaviorsSample 。