I have a dotnet core library, a framework 4.7.2 library and a vb6 application.
I want to write a common library for them all to access and so choose .netstandard2.0
I tried a the 4.7.2 framework wrapper library between .netstandard2.0 library and vb6.
However I ran into assembly binding problems
Looking at the docs I see
In .NET Core, the process for exposing your .NET objects to COM has been significantly streamlined in comparison to .NET Framework.
However no mention .netstandard2.0
I decided to try following the docs anyway even though my project is using .netstandard2.0
I got up to the instructions on Generating the COM Host in which case the output files ProjectName.dll, ProjectName.deps.json, ProjectName.runtimeconfig.json and ProjectName.comhost.dll should build.
However the ProjectName.comhost.dll and ProjectName.runtimeconfig.json do not create.
I see in this dotnet standard issue that Microsoft plans on having tooling support in "Preview 4"
I am running VS 16.4.5
[Update]
I decided to try making a .net core wrapper library and enabling it for com.
I was able to add my .netstandard to the wrapper library via a nuget package (I build the .netstandard library using azure devops)
When I build my wrapper library the .dll, .deps.json, .pdb, .runtimeconfig.dev.json and .runtimeconfig.json files are created in a bin\Debug\netcoreapp3.1 folder.
However none of the .netstandard library files appear in the bin\debug folder.
I copied the .netstandard library and the .netcore wrapper libraries to the same folder and ran
regsvr32 MyCoreComWrapper.comhost.dll
However no .tlb file is created which I need to be able to use from VB6
I note the following in the docs
Unlike in .NET Framework, there is no support in .NET Core for
generating a COM Type Library (TLB) from a .NET Core assembly. The
guidance is to either manually write an IDL file or a C/C++ header for
the native declarations of the COM interfaces.
I found some information on github but would love a step by step guide to making the .tlb
I thought about using latebinding instead but am unsure of how to use it with a com library.
[Update]
I put a sample project on GitHub including some VB6 files.
With VB6 referencing the .tlb referenced with the framework library.
When I try to run that I get
Could not load file or assembly 'Microsoft.EntityFrameworkCore, Version=3.1.2.0,
Culture=neutral, PublicKeyToken=adb9793829ddae60' or one of its dependencies. The system cannot find the file specified.
So I copied all the files from my framework test project to my vb6 folder, rebuilt and ran.
Then I got the error
Could not load file or assembly 'Microsoft.Extensions.DependencyInjection.Abstractions, Version=3.1.0.0,
Culture=neutral, PublicKeyToken=adb9793829ddae60' or one of its dependencies. The system cannot find the file specified.
I see the file Microsoft.Extensions.DependencyInjection.dll is present with File version 3.100.220.6706
Regarding the .NET standard, I may be wrong but I think this is not applicable here because the COM interop stuff are at a higher level than the one .NET standard is targeting; we can only talk about either .NET Core or .NET Framework for COM interop.
If you want to generate a type library, you have few options.
By far, the easiest method is just to use .NET Framework. The fact that you are wanting to create a type library negates the advantages of .NET Core already because several COM, especially the "Automation" features are Windows-only. Using framework will be fine at least until .NET Core 5 comes out.
That said, if you have a business reason for using .NET Core but still need COM support, including the type library, then based on this GitHub comment, you should be able to compile your own IDL. Note that requires you to install C++ build tools because the MIDL compiler is not really a standalone thing that you can get without the rest of the C++ build tools.
It is strongly suggested to have had read the documentation on how .NET Core handles COM activation.
Assuming having the C++ build tools is not a barrier for you, the steps would be the following:
1) Create a .idl file that defines all your COM interfaces in the IDL format. That requires some translation between the .NET interface and the COM interface. Here's a partial example of how you'd need to translate between your C# interface and COM interface as defined in IDL:
[
Guid("<some gooey>"),
InterfaceType(ComInterfaceType.InterfaceIsDual)
]
public interface IFoo
{
string Bar { get; }
string Baz(int Fizz);
}
Would be translated into IDL:
[
uuid(<assembly gooey>),
version(1.0)
]
library myFoo
{
[
uuid(<some gooey>),
object,
dual
]
interface IFoo : IDispatch {
[propget] HRESULT Bar([out, retval] BSTR* retVal);
HRESULT Baz([in] long Fizz, [out, retval] BSTR* retVal);
}
}
Once you've defined the .idl file and it is an accurate representation, you can then use MIDL to compile the .idl file into a .tlb file. Usually something like midl foo.idl /tlb: foo.tlb. You should make use of the MIDL language reference to help you write the .idl file. As a quick way to get started, you could copy your C# interfaces to a .NET framework project, use tlbexp, then use oleview (available via Visual Studio Developer Command Prompt) or olewoo to view the resulting IDL file to get you started.
The next step is to then create registry keys so that your CLSID can reference the type library. You will need to have your assembly's GUID handy and it must be used as the library's uuid in the .idl file as well.
Using IFoo interface example, you would need to create the registry similar to below (using .reg format for easy sharing/comprehension and assuming per-user installation, rather than per-machine):
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Classes\Interface\{<some gooey>}]
#="IFoo"
[HKEY_CURRENT_USER\Software\Classes\Interface\{<some gooey>}\ProxyStubClsid32]
#="{00020424-0000-0000-C000-000000000046}"
[HKEY_CURRENT_USER\Software\Classes\Interface\{<some gooey>}\TypeLib]
#="{assembly gooey}"
"Version"="1.0"
You will also need to create the registry in the CLSID, Interface, TypeLib, and Record as needed. This article provides a good overview of all registry keys but keep in mind it's assuming .NET framework, not .NET Core, so not all keys are applicable, especially under the CLSID branch.
Note that when you run the regsvr32, it will normally create the keys in the CLSID and Interface branches but you will need to add the TypeLib keys under the Interface's branch and also an entry to the TypeLib branch. You also will need to create the ProgId keys, too if you want to support CreateObject functionality.
Initially, you can start with just a .reg file that you can manually update & maintain but if you have several objects, then it becomes desirable to automate this. This can be also managed via the DllRegisterServer call so that when you execute regsvr32, it will take care of registering the keys. On the other hand, you're now polluting your codebase with registration code. Some elect to use installers to do the registry keys write instead.
I hope that helps you get started!
The issue is due to assembly binding resolution that fails when ran from VB6 (IDE or compiled .exe file).
Here are the steps to solve it:
Compile the VB project, for example, let's assume the compiled file is Project1.exe.
Copy all .NET assemblies (including x86 and x64 directories, and languages directory if localized version is important) aside the compiled VB6 file
Now run Project1.exe, you will get an error like this:
The error is clearly a mismatch between the version of your assemblies aside the Project1.exe file and the version of referenced assemblies (not references you've created yourself but reference embedded in these assemblies... ). You don't see that when you start a .NET program because resolution is a very complex process that depends on a lot of parameters (and it's not getting any better with .NET Core, Framework, Standard, nugets, etc.).
To futher check it's a mismatch error, you can also use the Fuslogvw.exe (Assembly Binding Log Viewer) tool from the SDK.
Now we know it's an assembly version mismatch issue, what you can do is create a file named Project1.exe.config aside Project1.exe and add assembly binding redirects to it.
The easiest way to configure it is to redirect all possible versions to the ones present in the directory that contains your program, so in your case (and as of today, as all these can evolve...), it would be something like this, possibly for every assembly you reference directly or indirectly:
<configuration>
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
...
<dependentAssembly>
<assemblyIdentity name="Microsoft.Extensions.DependencyInjection.Abstractions" publicKeyToken="adb9793829ddae60" />
<!-- 3.1.2.0 is the version of the assembly you ship -->
<bindingRedirect oldVersion="0.0.0.0-65535.65535.65535.65535" newVersion="3.1.2.0" />
</dependentAssembly>
...
</assemblyBinding>
</runtime>
</configuration>
Unfortunately, there are many satellite assemblies, and it's a bit tedious to create all redirects with correct information, so I've created a tool that creates a .config file with the redirects configured automatically for all .NET assemblies in a given directory: https://github.com/smourier/BindingRedirectGenerator.
If you want it to work for the VB6 IDE too, you'll have to use the same procedure in a VB6.exe.config file aside VB6.exe.
A reminder to myself
Use a demo UI to access the original DLL to confirm the call works. ( if you can't get it to work skip to making the App.Config for the unit test project using BindingRedirectGenerator )
Add a unit test in the com visible project to confirm the
call works.
Copy all the dlls created by both projects to the
release folder
For each com visible dll run as Administrator
c:\windows\microsoft.net\framework\v4.0.30319\regasm /verbose /codebase /tlb:MyLibrary.tlb c:\myproject\releasedlls\MyLibrary.dll
Install BindingRedirectGenerator to c:\brg say
At the command prompt change directory to c:\brg
BindingRedirectGenerator c:\myproject\releasedlls App.config
Rename App.config to MyVB6Project.exe.config and copy it to the same folder as MyVB6Project.exe
Remember to set up the files for the vb6.exe folder if you want to run it in the vb6 ide
Put the whole process in a script for future use ( I used a .bat)
Keep an eye on what nuget has put in app.config
Pay attention to the yellow warnings at build time!
Related
All question are related to a .net project dll in .net framework 2.0 that exposes itself as COM.
1) If we don't specify any GUIDs in the source code (typelib, classes, interfaces) who is generating the GUIDs? The compiler or regasm?
2) The GUIDs values exists in the dll, in the tlb or in both files?
3) Any developer with the same source code would generate the very same GUIDs independently on the machine where she builds or run regasm?
4) If I run regasm passing existing dll and tlb files, what happens If the dll and the tlb doesn't match? Regasm regenerate the tlb file with uptodate elements and GUIDs? Or it registers the TypeLib with the current tlb file?
5) What is the point of running regasm with dll and tlb parameters set?
Tlb file is part of what you deploy or it is best practice to only deploy the dll and let regasm generate the tlb on the fly?
6) And last question, is tlb really required? What is the point of having a tlb file? Is not all the information already in the registry? What extra info it provides?
7) When unregistering with regasm, what we need to provide? The dll? The Tlb? Both? What happens if dll (or tlb) doesn't match with existing reg entries? If already registered with tlb option but I run regasm unregister with dll only it would delete the TypeLyb entry too?
8) Regarding bitness, regasm will always generate entries under SysWow64 too? The regasm under Framework64 do the same as the one under Framework?
A type library is the exact equivalent of .NET metadata. It is most of all useful to the client programmer, it makes the compiler and the IDE smart about your library. Providing auto-completion and syntax checking so the odds of a mismatch between his code and yours are minimal. The registration step is necessary so your files can be found back. The type library is normally embedded as a resource in the DLL itself, like .NET metadata, but the .NET build model does not make that easy to do. The client compiler uses the type library info to generate the appropriate COM calls. Guids are a big deal because that is what the client compiler needs to use, identifier names play no role. There is a way to use "late binding" using names, the exact equivalent of Reflection in .NET, but that does not involve a type library.
who is generating the GUIDs?
The CLR does. Every .NET interface or class has one, regardless if it is [ComVisible(true)]. Exposed also through the Type.GUID property. If you didn't use the [Guid] attribute on the type then it runs an algorithm to generate the Guid that uses the type declaration as input. Or in other words, if you make any changes to the type then you can be sure that the Guid will have a different value. Which is the basic reason you should never use the [Guid] attribute, unless you have to create an exact drop-in replacement and cannot recompile client code. The TLBID comes from the AssemblyInfo.cs file that was auto-generated when you created the project.
in the dll, in the tlb or in both files?
It only exists in the DLL when you used the [Guid] attribute, but normally it is generated at runtime as explained above. It is always present in the type library, that's how the client compiler knows to create an object of your class and use its interface(s).
would generate the very same GUIDs
Yes, only the type declaration plays a role.
If I run regasm passing existing dll and tlb files
Regasm can only create a type library, as requested with its /tlb option, it cannot take an existing one. It otherwise does the exact same thing as Tlbexp.exe does, use Reflection to enumerate the types in the assembly to find the [ComVisible(true)] ones and generate the matching type library declaration. The extra thing it does is write the registry key for the type library to HKLM/Software/Classes/Typelib. So the client IDE can find it back.
What is the point of running regasm with dll and tlb parameters set?
No real idea with "dll parameter" might mean. As noted above, use /tlb to generate the type library. Whether or not you deploy the type library depends on its usage, if you don't also provide the client code then you should always deploy it so the client programmer can use it. Other usage of the type library is the subject of this post. If you're not sure how the client programmer is going to use your code then always deploy.
Is not all the information already in the registry?
What's in the registry is limited, only enough info to find the type library file back. The description of your interfaces, their method signatures, guids and the CLSID that the factory function needs is in the type library.
When unregistering with regasm, what we need to provide?
Exact same thing as registering it, you only add /unregister. You must also provide /tlb if you used it previously so the TypeLib registry key can be deleted. It can be pretty important to automate this while you are busy developing and testing the library, since the guids are normally auto-generated you can produce a lot of garbage in the registry. As well as ugly head-scratching when you forget to run Regasm. Project > Properties > Build tab, "Register for COM interop" checkbox. But with the downside that you have to run VS elevated so it can write to the registry.
regasm will always generate entries under SysWow64 too?
SysWow64 plays no role, do always avoid deploying to c:\windows. But yes, bitness does matter, the registry is structured so a 64-bit app cannot accidentally create an object in a 32-bit library and die on an ugly exception. And the other way around. A 32-bit client app will read registry keys from HKLM/Software/WOW6432Node, you only get your registry keys there is you used the 32-bit version of Regasm. Notable perhaps is that it is usually fine to run both flavors of Regasm, given that C# code can run on any platform.
We are working on a validation script for Kofax Capture 9.0 / 10.0 in VB.NET 3.5.
We know how to create a script using the Admin Module, and how to get it operational.
The problem is that we need to reference a dll, located on a remote machine. (GAC is no option) This dll holds abstract classes we need in each validation script.
Even when putting the dlls locally (copy local), the Validation Module (index.exe) immediately throws the "cannot find reference" exception, even though the project compiled perfectly.
I guess the basic question comes down to: where do we put the dlls, in order for the Validation Module to find them?
The simple answer is to put the dll in the same folder as the application because this is one of the places which .NET will probe when trying to find it. The Validation module is run from the Capture bin directory which will be something like "C:\Program Files (x86)\Kofax\CaptureSS\ServLib\Bin\". This would need to be done on each client using Validation.
If you have a more complicated scenario, you could look implementing the AppDomain.AssemblyResolve Event and using Assembly.LoadFile to get the assembly from a custom location, but the using the bin path is less complicated.
If you end up having further trouble, you can troubleshoot by using the Assembly Binding Log Viewer (Fuslogvw.exe) which can tell you more details about why the assembly failed to load and where .NET tried to search for it. Assembly loading can fail for reasons other than just the path.
For more detail on how .NET loads assemblies, see the following:
How the Runtime Locates Assemblies
Locating the Assembly through Codebases or Probing
We found a solution: add all library files as "links" to the project. (Add --> Existing File --> small arrow next to "Add" --> Add as Link)
This ensures the files are compiled when you build the project. The Kofax Validation Module can now find the files, whereas when referencing the file, it could not. Why it could not, remains a mystery...
I'm trying to get TFS team-build to reliably build a WPF C# app. This app relies on a VB6Lib.dll which we maintain, this VB6Lib.dll itself relies on other C# libs that we also maintain.
I've set up a build definition to build (in order):
VbDependencies.sln (all libs in this have com interop set, thus the VB6 can find their TLBs)
buildVB6Lib.proj (an msbuild file which calls "VB6.exe /make /d" to make the VBLib.dll on the build server, as part of this script I've been copying the VB6Lib.dll output to C:\tmp)
MainApp.sln (in my workspace, I've added a reference to C:\tmp\VB6Lib.dll)
Does this sound ok
?
On my dev laptop I usually build the VB6, copy its output to \tmp and then regsvr32 it there before adding a reference to it in my C# solution. It's this step that I'm not convinced my build def is doing.
Also, is there a way to get more useful output from the VB6 build, currently I get "Compile Error in File 'xxx.bas' Can' find project of library", but not which actual library it can't find.
You are correct in that the critical point in your build process on the development system lies in registering the COM object. However, one does not in general want to register the COM object on the build server, as this can cause all kinds of versioning issues and silent failures when the wrong COM object is registered or the registration fails.
The proper way to accomplish this is to generate an interop assembly manually and reference that instead of the COM object. This is accomplished with the tlbimp utility, for instance:
tlbimp ..\Libraries\VBLib.dll /out:..\Libraries\Interop.VBLib.dll
Run that command on your development system, then remove the reference to VB6Lib.dll and add a reference to Interop.VBLib.dll. You can then add the tlbimp command as a prebuild event in the referencing project so that the interop assembly is always build from the correct version, and you will never again need to have your COM object registered on the build system.
I am trying to set up communication between Centura and a COM .dll. (Downloaded from http://download.resip.fr for a database import)
Centura requires a .tlb file to be able to communicate to this component. Normally I would use regasm /tlb to generate the .tlb but seeing as it is a COM .dll this is not possible.
I found that I could use tlbexp for .NET dll's: http://msdn.microsoft.com/en-us/library/hfzzah2c(v=vs.80).aspx
I tried this out, knowing it would probably fail (as I have COM .dll). I received this error:
TlbExp : error TX0000 : Could not load file or assembly 'file:///C:\Windows\system32\ResipBcb.dll' or one of its dependencies. The module was expected to contain an assembly manifest.
Using Dependency Walker I noticed two .dll's missing. I found ieshims.dll online but I can't find the wer.dll. See this question.
I don't know if the tlbexp failure has anything to do with this file that is missing?
To sum up, my question is:
How do I get a .tlb from this .dll? I can't seem to find any way to extract the .tlb out of this COM .dll.
Best regards
Clint Cambier
What you are trying to do only works for .NET assemblies, not native COM servers. The type library for them is almost always embedded inside the DLL. In Visual Studio, use File + Open + File and select the DLL. Open the "TYPELIB" node, right-click the resource (usually 1), Export. Save it to, say, a project directory, use the .tlb filename extension.
TblExp and regasm are only valid on .NET assemblies, what you have is most likely a standard non .NET COM DLL. So neither of those two commands are valid on this DLL.
Standard COM objects are registered using regsvr32. Try running that against your DLL and see if it registers correctly. If it does you should see it listed in Centura's ActiveX explorer.
I'm using VS.NET 2010 integrated shell with F# and I'm trying to consume a soap web service... How do I go about generating F# source? I tried
wsdl l:"C:\Program Files (x86)\FSharpPowerPack-2.0.0.0\bin\FSharp.Compiler.CodeDom.dll" http://localhost/?wsdl
Along with
wsdl /language:"Microsoft.FSharp.Compiler.CodeDom.FSharpCodeProvider, Microsoft.FSharp.Compiler.CodeDom, Version=1.9.2.9, Culture=neutral, PublicKeyToken=a19089b1c74d0809"
However I can't seem to get the /language switch to work.
EDIT:
taspeotis' answer got me going... This generated F# source for the web service:
gacutil -i "C:\Program Files (x86)\FSharpPowerPack-2.0.0.0\bin\FSharp.PowerPack.dll"
svcutil /language:"Microsoft.FSharp.Compiler.CodeDom.FSharpCodeProvider, FSharp.Compiler.CodeDom, Version=2.0.0.0, Culture=neutral, PublicKeyToken=a19089b1c74d0809" http://localhost/?wsdl
Have you added FSharp.Compiler.CodeDom.dll to the GAC? Use gacutil.exe to do this.
3rd party edit
Here an example gacutil.exe /l System.XML.Linq to list certain assemblies.
Besides to FSharp.Compiler.CodeDom (source) an alternative might be the FSharp.Data library
Quote from jizugu: This generated F# source for the web service:
gacutil -i
"C:\Program Files (x86)\FSharpPowerPack-2.0.0.0\bin\FSharp.PowerPack.dll"
svcutil
/language:"Microsoft.FSharp.Compiler.CodeDom.FSharpCodeProvider
,FSharp.Compiler.CodeDom, Version=2.0.0.0, Culture=neutral
,PublicKeyToken=a19089b1c74d0809" http://localhost/?wsdl
This doesn't answer your question, but you may have better luck generating C#, compiling that C# into a library DLL, and referencing that DLL from your F# code. (The C# compiler csc.exe will be part of your .NET installation.)
I would be surprised if the F# Code DOM provider worked with WSDL. I wrote the initial implementation some time ago while at Microsoft and we got it to work with ASP.NET, but unless it has been improved since then, it probably won't work with WSDL or XSD.
Even for ASP.NET, we had to create a separate class that included some ASP.NET specific "hacks". This was partly because the CodeDOM generated by ASP.NET was invalid (in a way) and because the CodeDOM structure is not quite compatible with F#. If you really need to get this to work, you may have to add similar hacks (by modifying the source from CodePlex)
I tink that a safer approach is to include a small C# library project that generates the reference for you or invoking the C# compiler using csc.exe as Brian suggests.