void DeleteSelection()
{
foreach (var blfield in m_Blackboard.selection.OfType <BlackboardField>())
{
FieldModel field = (FieldModel)blfield.userData;
field.RemoveFromStruct();
}
}
void DeleteField(BlackboardRow field, FieldModel fieldModel)
{
fieldModel.RemoveFromStruct();
field.RemoveFromHierarchy();
SetModelDirty();
}