I would like to know how to display only needed item in tree view inside properties form in example Demo1
The property form in Demo1 uses the PropertyGrid control. This control displays the properties of an object. If you want full control of the properties displayed or even add properties at runtime you should take a look at the PropertyBag on codeproject.
The PropertyBag is able to simulate c# Properties and gives you much more control on “properties” displayed in the PropertyGrid.
For example it is possible to have an array of custom properties and display them in the PropertyGrid.