I have a DLL written in C# and set for COM visibility. I have it setup as a side-by-side assembly and can successfully deploy the application to client PCs registration free. My question is related to the development PC. Is it possible to compile against the DLL in a similar registration-free manner or is registration required on the development machine? I have tried adding the DLL directly though the Project -> References menu and get an error stating "Can't add a reference to the specific file." The DLL is sitting in the same directory as the .vbp file and I have tried adding the DLL both with and without the client app manifest being present.
I have tried adding the DLL directly though the Project -> References menu
That adds a reference to a type library. A type library is a language-independent description of the types in a COM component, VB6 uses it to know how generate efficient code and to provide type checking and auto-completion. A type library is the exact equivalent of metadata in a .NET assembly.
Traditionally, and the way VB6 did it, the type library was embedded as a resource in a DLL. So you are probably used to picking a DLL in the dialog. That however doesn't work so well when the DLL is generated by C#, the type library can only be generated after the C# code is compiled. You have to pick the .tlb file in the VB6 dialog. The traditional way starts with the COM component being described in the IDL language, the type library can be generated before the code is compiled so can easily be embedded in the final DLL. It is technically possible to do it in C# as well, but the build steps are very laborious and painful, you essentially have to build the DLL twice with different build commands.
The type library for a C# library is normally generated in one of three ways:
Using Project + Properties, Build tab, "Register for COM interop" option. This requires VS to run elevated so it can write to the registry. You start VS elevated by right-clicking its shortcut and picking "Run as Administrator"
By running Regasm.exe, using the /tlb:filename option. An alternative for the 1st bullet and necessary if you don't want to run VS elevated for some reason. Using the /codebase option on your dev machine is also wise to make it work exactly like the 1st bullet and not require putting the DLL into the GAC with gacutil.exe
By running the Tlbexp.exe utility, the type library exporter for .NET assemblies. No registration is done, it only generates the .tlb file.
The first bullet is the normal choice and very desirable because you can never forget to update the type library this way. It is perfectly fine on a dev machine since you only really care about reg-free deployment on the user's machine. You probably got into trouble by not doing this anymore.
Using the 3rd choice is okay and more compatible with your goals, run Tlbexp from the Visual Studio Command Prompt. Just keep in mind that you have to do it again when you make changes to your C# code. Forgetting this once and losing clumps of head-hair trying to figure out why your C# changes don't seem to be effective or getting hard-to-diagnose error codes gives you lots of reasons to consider the 1st bullet again :) You can emulate the reg-free scenario by running Regasm.exe with the /uninstall option.
Related
My software is written in VB6. For diagnostic purposes I need to determine the actual DLL / OCX files which are loaded and used by the application on a customer's computer.
Since VB6 DLLs (including OCX files) are COM libraries they are loaded indirectly based on information in the registry. This means it is possible that a different file is being used than what was used in development / testing environments. Sometimes in a client environment this can cause malfunctions which are hard to diagnose without this information.
(My plan is to build a diagnostic readout window in my program that shows the libraries that the program is using at that moment.)
You can use the Dependency Walker to find which DLL your program depend on.
But the OCX are not so easy to find because they are loaded at run-time based on the application dependencies and the registered components through the Windows registry. But you have to already know which OCX components your application references - from the Tools > References and all the places you call CreateObject.
There are many ways in which runtime dependencies on DLLs (or OCX files) can be established. Ideally you would need to account for all of them:
This answer is specific to VB6 but many other programming languages would work similarly.
Mechanisms which establish runtime dependencies:
At Compile time for traditional dynamically-linked libraries (DLLs which are not COM)
Files are (as their name suggests) dynamically loaded at runtime based on the linking process done at the end of compilation
This includes VB6 code which has used a statement like: Declare Function … Lib …
(In .NET this would mean calling out into “native code”)
To identify: Inspect the source code.
To identify without sources: These can be detected by a tool like Dependency Walker
At Compile time for COM DLLs
In VB6 this is known as “early binding”.
This includes VB6 code which has explicitly set a reference to a DLL or OCX.
Note that the dependency is actually on the COM class or interface GUID, and not explicitly on the DLL file itself.
To identify: These are listed in the project VBP.
To identify (alternate): If you don't have the VBP or source code, these dependencies can generally be revealed by by IMPORT statements in OLEView. You might need to look up some GUIDs from there in the registry to see what actual DLL files are used.
At Compile time for statically-linked libraries (not COM, not DLLs)
Library code is included in the EXE or DLL which is being compiled. Therefore there is no runtime dependency to anything external.
As far as I am aware, this is not possible for VB6 programs. Something like a C linker could use libraries like this. A rough equivalent in .NET would be using ILMerge to combine assemblies.
At Runtime for traditional DLLs (not COM)
DLLs can be loaded arbitrarily using Win32 API such as LoadLibrary().
To identify: You have to look at the source to know what might happen.
Alternately if you don't have the source you could use tools like Process Explorer and/or Process Monitor to observe a running instance and see what DLLs actually get loaded.
At Runtime for COM DLLs
Classes can be loaded arbitrarily using eg VB6 CreateObject() calls.
In VB6 this is known as “late binding”
Which DLL will be used to provide the class will be determined by the process’s activation context. The activation context is established by the app manifest file (if there is one) or the Windows registry otherwise (the normal default for VB6 programs).
To identify: You have to look at the source to know what might happen. You also need to know what the configuration state will be on the PC that runs the code - which DLL files are registered, assuming a manifest is not used.
Alternative for no source code: as in the case above
Important: dependencies can be chained. So really you need to "walk the links" of all the dependencies until you build up a complete mapping of what is required. Somewhere in that mapping you can draw a line between what you need to deploy and what the operating system or other runtime environment can be relied on to provide. (IMO for VB6, that line should be drawn rather liberally).
You may be thinking that all this makes the task very difficult or tedious – I totally agree. :)
I have a project that I am developing that uses a third party COM library as a reference and I would like to build this project on a Visual Studio Team Services build client. My first idea is to create a MSBuild task that checks to see if the COM library is installed on the local computer and if it is not, go ahead and install it, but this seems like a really messy way to do this. I have searched around but it seems as though all the answers date back years and I can't seem to make the few I have found work in a VS 2013 project. How have other people solved this problem? Is there a cleaner way?
For reference I have also tried this solution, which looks really clean, to no avail.
I would go one of these routes:
Generate interop dll with tlbimp, add it to your project and reference it directly:
In VS command prompt, execute tlbimp.exe <your_dll> to generate the interop dll. You can specify the name with /out option.
put this dll somewhere with your code
reference it by going to Add reference > Browse and click Browse... to add the dll
Generate the tlb from COM dll , add it to the project and reference the tlb:
Generate the tlb (e.g. using OLE/COM Object viewer) or extract it from the dll resources,
put this tlb somewhere with your code
reference it by going to Add reference > COM and click Browse... to add the tlb reference to project
As #HansPassant noted in comments, this solution still relies on registry, but you can register it with regtlb, regtlib or similar tool, as a prebuild step, which should be easier than installing the server (though if it is just a dll, you could use regsvr32 to register it instead of full install). However, this is still more complex than the approach with interop dll
I'm forced to use a third-party COM component in an application, and I'm having issues adding the reference to my project.
I've added this DLL as a reference to a project before, but in the past it would link directly to the DLL, such that the "Path" in the reference's properties would be filesystem path where the DLL was installed (i.e. not relative to my solution's directory). However, now, when I add the reference, the "Path" is to my project's obj directory, "Embed Interop Types" is set to True, and it's listed as an ActiveX component (which is not correct).
Then, I stumbled upon this MSDN article, which says:
If you want to add a reference to a registered COM DLL that contains an internal manifest, unregister the DLL first. Otherwise, Visual Studio adds the assembly reference as an ActiveX Control instead of as a native DLL.
Well, there you have it. That's my exact problem. I need the native DLL, but I'm getting an ActiveX Control instead. So, I did as it suggested and unregistered the DLL. However, when I then try to add the reference, I get an error saying:
A reference to ... could not be added. Please make sure that the file is accessible, and that it is a valid assembly or COM component.
If I register the DLL again, I'm able to add it as a reference, but again, it's added as an ActiveX control. At this point, I don't know what else to do. Microsoft is very clear that I must unregister it before adding it as a reference, but then Visual Studio 2013 apparently won't let me add an unregistered DLL. Any one have any idea how to work around this?
UPDATE
So, apparently a recent update to this app made COM the only option (no directly using the DLL). The fact that it was added as ActiveX didn't mean anything. The problem turned out to be that this was a 32-bit library trying to run in 64-bits. I knew that was a potential problem, but switching the platform target to x86, still resulted in an error so I ended up chasing a red herring. Turns out IIS Express 8 runs natively as 64-bits even if the platform target of the site you're debugging is 32-bit. I had to go into Visual Studio options and uncheck the flag that tells IIS Express to run 64-bit (under "Web Projects") and then everything ran fine.
So, since adding the registered DLL was pretty much a no-go, I focused instead on trying to figure out why Visual Studio wouldn't let me add it when it was unregistered. I mean, sure, I might get an error about it being an unregistered DLL once I tried to run the project, but it should at least let me add it as a reference, regardless.
I eventually stumbled upon tlbimp.exe, which according to Microsoft:
The Type Library Importer converts the type definitions found within a COM type library into equivalent definitions in a common language runtime assembly. The output of Tlbimp.exe is a binary file (an assembly) that contains runtime metadata for the types defined within the original type library.
Okay. Well anyways, I opened a Visual Studio Developer Prompt (regular cmd doesn't have tlbimp.exe on the path), and ran my DLL through it. It created a new DLL, which I was able to add as a reference, and it satisfied my project dependencies. However, I haven't tested it just yet to make sure everything still works as it should once this thing is running, so I'll update with what I find there.
UPDATE
Yeah, so this doesn't work either. I get the same error once it's running saying that the class is not registered. Only now, I can't register this DLL because tlbimp.exe removes the entry-point.
This is driving me crazy. I have developed a .NET COM DLL that is used by a VB6 DLL wrapper in order to update and replace some legacy functions in an application.
I am now trying to remove the requirement to use regasm on client machines so have worked out how to do that on a test DLL which all works fine.
I branched the DLL just in case and added an app.manifest file. Everything else worked out fine and I got it all working. The manifest is embedded and Visual Studio 2012 generates a mydll.dll.manifest file in the release folder.
Then I went back to the original trunk and added an app.manifest file (no point in merging as there were no code changes). I copied the contents of the branch into the app.manifest file and built the release version. The manifest is embedded in the DLL but no mydll.dll.manifest file is generated.
I know that it's not strictly necessary to have the mydll.dll.manifest file but I'd like things to be consistent (and for some reason the test process doesn't produce the same results with the trunk version) so how can I force it to be created?
This is a VB.NET DLL project so it doesn't have (or I can't find) the 'Generate Manifest' property drop down mentioned in the first answer here. How can I set this? Or is there a way to set it by editing the project file directly?
References:
Original walkthrough article and some corrections.
Overview by Junfeng Zhang in two articles plus a useful tool
You are making a fairly common mistake. A reg-free COM manifest helps an application find a COM server without looking in the registry to locate the DLL. Embedding the manifest in the DLL is like trying to solve the chicken and egg problem, Windows cannot possibly find that manifest if it cannot locate the DLL first.
The manifest needs to be part of the client app. Which is tricky since it is VB6, it doesn't support embedding manifests in its executables.
You could tinker with the mt.exe tool, an SDK utility that supports embedding manifests in an executable. You'd have to run it by hand after building the VB6 binaries. That's unfun and very likely to cause trouble when you forget. It is in general not a joyful tool to use, documentation is meager, incomplete and unhelpful, a chronic problem with manifests.
The fall back is a separate app.exe.manifest file, what Windows will look for next when it cannot find a manifest embedded in the executable. Where "app.exe" must be renamed to the name of the VB6 program. The EXE, not the DLL. This now also gives you a chance to avoid having to register the VB6 DLL, presumably what you really want if you truly want to make your program run reg-free. The disadvantage is that it will not work when you debug your VB6 program, wrong EXE. You'd also need a vb6.exe.manifest, located in the VB6 install directory.
Needless to say perhaps, very hard to get ahead with VB6 here. It just wasn't made to help you do this, they didn't have a time machine in 1998.
I have to admit that I don't know VB at all, but in the case of C++ and C# Visual Studio projects I previously had to resort to calling mt.exe in a post-build step in order to get the DLL manifest I wanted. Maybe that workaround would work in your case as well?
I have one problem in vb6. I created a .tlb file in VB.net 2005 by adding Com class to project. I built the project, I got .tlb file and .dll files while building project, i selected "Register for Com interop" from project properties and built. It registered autometically and I can use created .tlb file in that PC in Vb6 working fine. if I deploy application to another PC and run I am getting "Error 429 ActiveX Component Can't create object" run time error. What I need to do? Please help me as soon as possible. I can't deploy the application to client due to above error.
one possible solution is to install .net frame work on client pc i never want to install .net framework any other solution will be most appreciatable.
If you've created a DLL in a .NET language (such as VB.NET), the target computer must have the .NET Framework installed in order to use the DLL.
This a hard and fast requirement, irrelevant of how you're utilizing the DLL, whether from a VB 6 application through COM interop or otherwise. It is also a hurdle you'll have to jump over first, before you worry about things like registering COM components, as Uday's answer suggests.
If you don't want a dependency on .NET, you need to use another environment to create the ActiveX DLL; either C++ or VB 6 are possible choices.
One option may be that, while deployment, you need to register that .tlb file in System Registry using regsvr32 command in command-prompt. Generally static libraries does not work until they are registered with System Registry.
You might have seen many programs register components during installation like 'Registering Type Components' or 'Registering COM Components' (for those who do networking especially). Those components are nothing but native COM dlls and tlbs.
so when creating deployment project, add some scripting login to register thode dlls and tlb to System registry using:
regsvr32 <path to tlb/dll>
you have to recursivey call this command for every dll/tlb you want to register with system. For example, if you have 4 dlls and 2 tlbs then you have to call it 6 times providing the path of dll and tlb one at a time.