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Cleanup phase, don’t forgetrelease the value// when is not needed any moreif (MessageArg) {session->ReleaseValue( MessageArg ) ;}Calling the PowerBuilder NVOfrom .NET Managed CodeNow we know how to call PBNI inC++ unmanaged code. The next step isto export the methods from the C++DLL and declare proper C# prototypesto make it available for C#. The__declspec(dllexport) modifier tells thecompiler to make the function visible(export) to other applications, so thatother applications can call this method.Listing 2 exports the PBInvoker class asDLL functions.Note: To check if the methods areproperly exported, you can use dumpbin.exeto see if the function names arein the list; here is an example of theoutput of dumpbin.exe showing theexported symbols:dumpbin /exports PBInvoker.dll1 0 000115B4 _PBX_GetVersion@02 1 0001162C barcode4 3 000115FF closePBSession5 4 000116BD initPBSessionParameter Marshaling from.NET to Unmanaged CodeThe .NET Framework uses managedcode, which is an interpreted instructionset, similar to Java bytecode orPowerBuilder P-Code. The C++ DLL usesunmanaged code, which is machinecode. This introduces an issue becausethe data types in the .NET Frameworkneed to be marshaled (meaning convertbetween the C/C++ data type formatand the .NET data type format) to passback and forth between managed andunmanaged code. C# provides themeans to do this job.In this example, we need to callthree C++ DLL methods in C#:void initPBSession(LPCTSTR libList[],int libNum, LPCTSTR appName);void closePBSession();void barcode(LPCTSTR specimen_formatted, LPCTSTR spcimen_id,char *code);First, we need to tell C# that thesethree methods are from an unmanagedDLL. This is done by using the[DllImport] attribute tag in the functionprototype in C#. Also don’t forget to use“PBNI offers a goodsolution to reusePowerBuildercomponents in the.NET Framework”the “extern” keyword, meaning thefunction exists outside the C# module:// pbinvoker.dll is the DLL file name[DllImport("pbinvoker.dll",CharSet=CharSet.Auto)]public static extern void closePBSession();Second, we need to use the proper[MarshalAs] attribute options to definethe marshal behaviors for LPCSTR[],int, LPCSTR, and char* unmanaged C++parameters. The following code showshow to define the marshal behaviors forthose three DLL methods:[DllImport("pbinvoker.dll",CharSet=CharSet.Auto)]public static extern voidinitPBSession([MarshalAs(UnmanagedType.LPArray, ArraySubType=UnmanagedType.LPStr)]string[]libList,int libNum,[MarshalAs(UnmanagedType.LPStr)]string appName);[DllImport("pbinvoker.dll",CharSet=CharSet.Auto)]public static extern void closePBSession();[DllImport("pbinvoker.dll",CharSet=CharSet.Auto)]public static extern void barcode([MarshalAs(UnmanagedType.LPStr)]stringspecimen_formatted,[MarshalAs(UnmanagedType.LPStr)]stringspcimen_id,// Use C# StringBuilder for outputstring buffer[MarshalAs(UnmanagedType.LPStr)]StringBuilder code);There are some interesting things Ineed to point out:1. [MarshalAs(UnmanagedType.LPArray,ArraySubType=Unmanaged-Type.LPStr)] is the way to marshalLPCTSTR[]. It tells C# the array typeand element type in C++, which is apointer array and a C string pointerin each element in our case.2. [MarshalAs(UnmanagedType.LPStr)]StringBuilder is the way to marshalan output string buffer. The String-Builder should have enough space tohold the return value from the DLLmethod; you can allocate the spacefor the StringBuilder and then call theDLL method in C#.Here is the C# code to invoke theDLL methods:// allocate buffer for the outputstringStringBuilder buf = new String-Builder(256);// Init PBInvoker, automation is thePowerBuilder application object nameinitPBSession(new String[] {"automation.pbl"},1, "automation");// Call the methodbarcode("C05-10", "tpro402137", buf);Console.Out.WriteLine("sb = {0}", buf);// Clean upclosePBSession();Creating a GenericPowerBuilder Invoker for C#We have discussed some basic techniquesfor using PowerBuilder NVOs inC#. One interesting idea is to create atool to generate both the C++ proxyDLL and C# prototypes based on theselected NVOs and methods. To generatethese proxy files, all we need is a listof NVOs in the PBL and prototypes ofeach method. Fortunately, pbsig100.exedoes it for us. We can parse the outputof pbsig100.exe to retrieve the metadataof any PBL file. The rest of the work is togenerate the source code based on theprototypes, which is fairly easy to do. I’llcover the details of the code generationin a follow-up article.ConclusionPBNI is a great innovation in Power-Builder. It opens a brand new space fordevelopers to reuse and extend Power-Builder. PBNI offers a good solution toreuse PowerBuilder components in the.NET Framework.To find more information aboutPBNI, please reference the PBNI SDKdocument and CodeXchange for examples.▼david.huo@sybase.com28 PBDJ volume12 issue11pbdj.sys-con.com
Listing 1// Define the function pointer for PB_GetVMtypedef PBXEXPORT PBXRESULT (*P_PB_GetVM)(IPB_VM** vm);// constructorCPBInvoker::CPBInvoker(LPCTSTR LibList[], int libNum, LPCT-STR appName){_hinst = NULL; // a member variable to hold the DLL handleIPB_VM* pbvm;_hinst = LoadLibrary("pbvm100.dll"); // step2: load PBVMif ( _hinst == NULL ) {throw "Loaded PBVM successfully";}// step 3: Get PBVM referenceP_PB_GetVM getvm =(P_PB_GetVM)GetProcAddress(_hinst,"PB_GetVM");if (getvm == NULL) {throw "PB_GetVM failed";}getvm(&pbvm);if (pbvm == NULL) {throw "getvm failed";}// step 4: Create IPB_Session instance, LibList is anarray holds the pbl file namesif ( pbvm->CreateSession(appName, LibList, libNum, &_session)!= PBX_OK ) {throw "Error in CreateSession";}}// destructorCPBInvoker::~CPBInvoker(){// step 13: Release IPB_Sessionif( NULL != _session ) {_session->Release();}// unload PBVM DLLif( NULL != _hinst ) {FreeLibrary(_hinst);}}// Call the NVO methodvoid CPBInvoker::barcode(LPCTSTR text, LPCTSTR format,char* code){// step 5: Find the group, n_automation is the NVO’snamepbgroup group = _session->FindGroup("n_automation",pbgroup_userobject);if (group == NULL) throw "n_automation is not found!";// step 6: Find the class, n_automation is the NVO’snamepbclass cls = _session->FindClass(group,"n_automation");if (cls == NULL) throw "n_automation class notfound!";objectpbobject pbobj = _session->NewObject(cls);// PBCallInfo contains arguments and return valuePBCallInfo ci;// step 8: GetMethodID to get the method. “SSS” is thesignature string, fn_barcode is// the function namepbmethodID mid = _session->GetMethodID(cls, "fn_barcode",PBRT_FUNCTION, "SSS");// step 9: Initialize call info structure based onmethod ID_session->InitCallInfo(cls, mid, &ci);// step 10: Fill in parameters.ci.pArgs-> GetAt(0)->SetString(text);ci.pArgs-> GetAt(1)->SetString(format);// step 11: invoke the method_session->InvokeObjectFunction(pbobj, mid, &ci);// step 12: Retrieve the return value, code is a validmemory// buffer passed in by the callerpbstring ret = ci.returnValue->GetString();strcpy( code, _session->GetString(ret) );}// step 13: Release the PBCallInfo structure_session->FreeCallInfo( &ci );Listing 2#define PBINVOKER_API __declspec(dllexport)PBINVOKER_API void barcode(LPCTSTR specimen_formatted,LPCTSTR spcimen_id, char *code){// _invoker is a global variable holds the reference ofthe PBInvoker objectif( NULL != _invoker ) {// call the NVO method_invoker->barcode(specimen_formatted, spcimen_id, code);}}PBINVOKER_API void initPBSession(LPCTSTR libList[], intlibNum, LPCTSTR appName){// init the IPB_Sessionif( NULL == _invoker ) {// instantiate the CPBInvoker wrapper class_invoker = new CPBInvoker(libList, libNum, appName);}}PBINVOKER_API void closePBSession(){// clean upif( NULL != _invoker ) {// delete the wrapper objectdelete _invoker;_invoker = NULL;}}// step 7: Create an instance of the PowerBuilderpbdj.sys-con.comPBDJ volume12 issue1129
Page 5 and 6: HAMMER THECOMPETITIONWITH POWERBUIL
Page 9 and 10: Never write another SQL insert, upd
Page 11 and 12: THE STRAIGHT GOODS ON EAServer.BRIN
Page 13: © 2003 Sybase, Inc. All rights res
Page 17 and 18: ment data in the “system table”
Page 20: use the KeyDown ( ) method in Power
Page 23 and 24: TMTMENGAGE AND EXPLORE...The Techno
Page 26: 2. GetAt obtains the value at a spe
Page 31 and 32: from within PowerScript and capture
Page 33 and 34: We call PostURL with our additional
Page 35: Forget the wires.We knowthe ropes.W

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