Painting PDF-417 2d Barcode In Java
Using Barcode maker for Java Control to generate, create PDF 417 image in Java applications.
extra code doesn't create a big performance hit, but it does bloat the executable If you keep your executable small, your application has fewer page exceptions on startup and performs better in low-memory conditions If you use lightweight objects, you have full control of your object You might as well take advantage of this control by telling VB not to expect an error return from a given function The code is more efficient, and it's easier to write
Bar Code Generation In Java
Using Barcode encoder for Java Control to generate, create bar code image in Java applications.
Returning Errors from Lightweights
Barcode Reader In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
COM methods indicate error values by returning HRESULT error codes VB functions use structured exception handling to return errors across functions COM specifies that methods must not raise exceptions across a vtable boundary VB raises errors by throwing exceptions across function boundaries Lightweight objects are in a precarious position between these two error-handling approaches VB functions are easily divided into two categories: those in a standard module and those in a class module All functions in standard modules (except the Sub Main entrypoint) assume that there is another VB function above them to catch any errors they might throw After all, the only valid entrypoints into a VB process are Sub Main and vtable entries on public COM objects All VB class module functions are equipped to catch errors, so procedures in standard modules assume that they are never in danger of throwing an error that can't be caught This is one of the main reasons why hacking a DLL to expose direct entrypoints is very dangerous: if an error gets by you, you can easily take the calling EXE down (the second reason is thread initialization, which I'll discuss in 13) A Public function in a class module cannot assume that the caller can catch a thrown exception For this reason, class module functions actually catch their own errors and translate them into HRESULT return values before the function completes The class module function always returns control to the caller the same way, regardless of the error state VB deals with exceptions better than HRESULTS, so any error HRESULT returned by a method on a COM object is translated immediately into an exception and thrown
Draw PDF 417 In Visual C#.NET
Using Barcode encoder for .NET framework Control to generate, create PDF 417 image in .NET framework applications.
Make PDF-417 2d Barcode In .NET Framework
Using Barcode printer for ASP.NET Control to generate, create PDF417 image in ASP.NET applications.
Vtable functions in a lightweight object are actually COM methods, so they should never let an untrapped error escape from the function You should be religious about following this rule if the lightweight is aggregated as part of a publicly exposed object But if you break this rule when the object is used only from internal code, you won't actually break anything because VB is ready to catch any error you throw at it In fact, you beat VB at its own game because it's about to throw an exception derived from the HRESULT return anyway Raising untrapped errors directly is easy, but returning the correct HRESULT from the function is not quite as straightforward By the time the error trap sees an error, VB has already adulterated the information by mapping some standard errors to VB error numbers, and stripping the top 16 bytes off all VB error numbers to turn them into the friendly numbers you are used to seeing All VB error numbers are in the range &H800A0001 to &H800AFFFF (called the FACILITY_CONTROL range), but the VB Err object shows this range as &H00000001 to &H0000FFFF The VB error numbers are nice to work with because of their compressed size However, the rest of the COM world, including VB in the role of caller, does not consider these values error numbers because the SEVERITY_ERROR bit (&H80000000) is not set You need to put the high bits back into the error number before returning it from a lightweight method in order to convince any callers that it is indeed an error value The following function is good enough for almost all purposes, although it doesn't contain an advanced reverse-map for performing transformations such as mapping Error 7 (Out of memory) to the system standard &H8007000E (E_OUTOFMEMORY) In addition to being poorly defined (VB maps multiple system errors to a single VB error), the complete reverse error map is large and undocumented This won't affect most applications, but you can easily add a Select Case statement to the provided MapError function if you need special handling for specific error values Public Function MapError() As Long Dim Number As Long Number = ErrNumber If Number Then If Number > 0 Then Number = &H800A0 000 Or Number
Painting PDF-417 2d Barcode In .NET
Using Barcode generation for VS .NET Control to generate, create PDF417 image in .NET framework applications.
Generate PDF-417 2d Barcode In VB.NET
Using Barcode creator for VS .NET Control to generate, create PDF 417 image in .NET applications.
UCC.EAN - 128 Encoder In Java
Using Barcode creator for Java Control to generate, create USS-128 image in Java applications.
Barcode Printer In Java
Using Barcode maker for Java Control to generate, create barcode image in Java applications.
Creating Delivery Point Barcode (DPBC) In Java
Using Barcode printer for Java Control to generate, create USPS POSTal Numeric Encoding Technique Barcode image in Java applications.
Bar Code Creator In VB.NET
Using Barcode printer for .NET Control to generate, create barcode image in VS .NET applications.
Print Barcode In VS .NET
Using Barcode maker for ASP.NET Control to generate, create barcode image in ASP.NET applications.
Drawing Barcode In Visual Studio .NET
Using Barcode maker for ASP.NET Control to generate, create barcode image in ASP.NET applications.