How can Property Descriptor gets values of two controls using same code line?

Question

I found this code in one of the project developed by an Ex-Employee for custom gridview with custom controls which works fine but I am not sure what exactly it is doing,

Answer 1

GetValue(control.NamingContainer, this._PropertyAField, ref propertyA)

ProperyA is given as a reference therefor everything that happens to propertyA inside that method will update propertyA that was defined above.

using

PropertyDescriptor propertyA = null;

instead of

PropertyDescriptor propertyA = TypeDescriptor.GetProperties(DataBinder.GetDataItem(control.NamingContainer)).Find("boundField", true);

will still work.

Further Reading
ref method parameter keyword