public void Process( )
{
_treeItem.AddBehaviour(_behaviour);
CustomProperties customProperties = _treeItem.ItemProperties.CustomProperties;
var form = new AddCustomPropertyForm(e => !customProperties.ContainsKey(e));
DialogResult result = form.ShowDialog( );
if (result == DialogResult.OK)
{
IoC.Model.AddCustomProperty(_treeItem, form.NewCustomProperty);
}
}