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!
I'm using the EPPlus library in a Visual Studio 2012 SharePoint 2010 project and get the following 'file not found' exception from an Application Page when I add "ExcelPackage pck = new ExcelPackage();" as the starting point of creating an excel file:
Could not load file or assembly 'EPPlus, Version=3.1.3.0, Culture=neutral, PublicKeyToken=ea159fdaa78159a1' or one of its dependencies. The system cannot find the file specified.
The library registers without a problem and the project builds and runs until the function containing the EPPLus code is called.
The same code works fine on the same machine in a standard asp.net web application.
Any suggestions appreciated, thanks.
You need to deploy the Assembly in the GAC.
You can add it using something like GacUtil or include the assembly in your solution by adding it to the solution package.
In solution explorer, double click on Package.
In the Package properties select the Advanced tab
Add the assembly in Additional Assemblies
If you are trying to access this library inside inline code in an ASPX page (e.g. between <% and %> tags), then you'll need to add a reference to the assembly in the web.config so when the page is compiled on demand, the compiler will reference it.
<compilation debug="true">
<assemblies>
<add assembly="EPPlus, Version=3.1.3.0, Culture=neutral, ..." />
I am working on a vb.net application that uses SQLite and since it was compiled against the version 2 of the .net framework, i added this line to my config file
<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
</startup>
My final objective for the application is to make it a standalone, so not a single file except the exe (well the application will generate a file for the database, but my point is i want the user to only download 1 single file).
And i noticed that when i build it, the config file is always copied, and if i run the application without the config file, i would get the uncaught exception "legacy" error..
Is there any way to either include that config during runtime? or perhaps catch some type of exception to prevent that dialog from showing up and scaring the user (i know this probably not the best approach)
I have searched and found other similar problems on SO but none of the questions i found got to a solution that worked for me so i would appreciate your help.
While it is possible to set the legacy runtime policy at runtime, I would recommend deploying as an installer.
well the application will generate a file for the database, but my point is i want the user to only download 1 single file
They could download your installer, which could take care of setting up everything correctly. This is likely to be required in any case, as SQLite will need its own DLLs as well as your .exe to be there in the deployment.
I am unable to use the WCF Test Client. I always get the following error.
Error: Cannot load reference assembly 'C:\Windows\Microsoft.Net\assembly\GAC_32\System.Data\v4.0_4.0.0.0__b77a5c561934e089\System.Data.dll'
Cannot load file C:\Windows\Microsoft.Net\assembly\GAC_32\System.Data\v4.0_4.0.0.0__b77a5c561934e089\System.Data.dll as an Assembly. Check the FusionLogs for more Information.
Could not load file or assembly 'file:///C:\Windows\Microsoft.Net\assembly\GAC_32\System.Data\v4.0_4.0.0.0__b77a5c561934e089\System.Data.dll' or one of its dependencies.
This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.
I'm not having any luck finding a solution on google. I'm hoping that the stackOverflow hive brain can help.
Thanks.
If I'm not mistaken, you need to add the runtime version setting in your app.config file's <configuration> element:
<startup>
<requiredRuntime version="v4.0.30319" />
</startup>
I have an application which is being developed in VS2010, and makes use of the Castle-Windsor IoC, through a configuration file.
One of the components I am registering, also developed in VS2010, references a .net 2.0 component (LeadTools), so recompiling the 2.0 project isn't an option. When the wrapping component's registration is done, a "ComponentActivatorException" is raised, which wraps a "System.TypeInitializationException", which in turn wraps a "System.IO.FileLoadException" with a message of "Mixed mode assembly is built against version 'v2.0.50727' of the runtime and cannot be loaded in the 4.0 runtime without additional configuration information."
I have added the runtime declaration to the application's configuration file, as so:
<!-- useLegacyV2RuntimeActivationPolicy is needed for LEADTools-->
<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
<supportedRuntime version="v2.0.50727" />
</startup>
This works fine if the wrapping component isn't registered in Windsor, however, it does appear to disregard the directives otherwise.
Thanks!
I assume you're using registration via XML?
What happens if you register the component in code?
Can you try to reproduce the issue without error?
call Type.GetType("assembly qualified name of the type from .net 2.0 assembly");
The problem was due to using "define"s and "if"s within the configuration file, per the MicroKernel documentation. Removing all of those elements from the App.Config file allowed the components to be instantiated, whether or not they were registered in the Windsor container.