There are some important limitations on the code you can enclose in conditional compilation blocks.

• Case sensitivity � PowerScript is case insensitive, but C# is
  case sensitive. If a resource has the same name as another resource
  with differences only in the case of one or more characters, PowerBuilder cannot
  process the resource names correctly.
• Calls to PowerScript from .NET functions � you cannot call a .NET method inside a conditional code block
  if that method calls back into PowerScript functions.

• Delegates are not supported � a delegate is a type that safely encapsulates a method, similar
  to a function pointer in C and C++. You cannot
  use delegates in conditional code blocks.
• .NET classes and interfaces � you cannot use .NET classes and interfaces as parameters
  to functions and events.
• Inheriting from .NET classes � you cannot create user objects, windows, or window controls
  that inherit from .NET classes.
• Implementing .NET interfaces � you cannot create user objects that implement .NET interfaces.
• Consuming .NET generics � you cannot consume .NET generic classes or generic methods
  in conditional code blocks. The .NET Framework 2.0 introduced generics
  to act as templates that allow classes, structures, interfaces,
  methods, and delegates to be declared and defined with unspecified
  or generic type parameters instead of specific types. Several namespaces,
  such as System Namespace and System.Collections.Generic, provide
  generic classes and methods.

  The System.Nullable type is a standard representation of optional
  values and as such it is also classified as generic and therefore
  cannot be consumed in PowerBuilder .NET applications.

  In .NET Assembly and Web service targets, you can select a
  check box to map PowerBuilder standard datatypes to .NET nullable
  datatypes. Nullable datatypes are not Common Type System (CTS) compliant,
  but they can be used with .NET Generic classes if a component accepts
  or returns null arguments or if reference arguments are set to null.

• AutoScript does not support .NET classes � AutoScript works as expected for PowerBuilder objects, properties,
  and methods inside conditional code blocks, but it does not display
  for .NET classes.

• DYNAMIC and POST do not support .NET methods � you cannot use the DYNAMIC or POST keywords when you call
  a .NET method.

• 
  .NET arrays of arrays � .NET arrays of arrays are supported in conditional code blocks
  for .NET targets only.