Workflow Foundation 4.0 has very good support for custom activity development. We can have our own custom activity with very good look and feel. When you define a custom activity, one of the main requirements is how to manage the associated properties in the property grid. We can either use the TypeConverter or PropertyValueEditor for managing the properties and associated editors in PropertyGrid. TypeConverters are same as those in WPF. PropertyValueEditors are similar to the PropertyEditors in WPF, which provides custom editor for our property. For more, please refer http://www.dotnetfunda.com/articles/article1118-workflow-foundation-40–propertyvalueeditor-.aspx