The third step is to create a “tree” control in the main form, the control relationship with the “attribute defined in step one “ in the Form Design (See 7.1.2.10.2). See the description below.
Hold down the left mouse button on the tree control in the control list, and then drop the mouse in the row or cell (marked by yellow area)
To control the tree with the attribute, first click the mouse control, then click on the “Data Member” section and click the button 
to select the associated attribute.
By selecting the button , the “object selector” that contains the attributes defined in the entity is displayed.
