Unsupported system functions in Windows Forms

Table 11-3 lists categories of system functions that are not supported in Windows Forms applications.

**Table 11-3: Unsupported system functions by category**
Category	Functions
DDE functions	CloseChannel, ExecRemote, GetCommandDDE, GetCommandDDEOrigin, GetDataDDE, GetDataDDEOrigin, GetRemote, OpenChannel, RespondRemote, SetDataDDE, SetRemote, StartHotLink, StartServerDDE, StopHotLink, StopServerDDE
Garbage collection functions	GarbageCollectGetTimeLimit, GarbageCollectSetTimeLimit
Input method functions	IMEGetCompositionText, IMEGetMode, IMESetMode
Profiling and tracing functions	TraceBegin, TraceClose, TraceDisableActivity, TraceDump, TraceEnableActivity, TraceEnd, TraceError, TraceOpen, TraceUser
Shared Object functions	SharedObjectDirectory, SharedObjectGet, SharedObjectRegister, SharedObjectUnRegister

Post function Post function calls with reference parameters are not supported.

IsNull function In .NET applications, if you call the IsNull function with a variable of a reference type (a type derived from the PowerObject base class) as the argument, IsNull returns true if the variable has not been initialized by assigning an instantiated object to it. To ensure consistent behavior between standard and .NET PowerBuilder applications, use the IsValid function to check whether the variable has been instantiated. For more information, see the description of the IsNull function.