svcutil: System.NullReferenceException while generating duplex client

[lipchev]

Describe the bug
I'm receiving a System.NullReferenceException (here) while attempting to generate a duplex proxy in a .net5.0 project.

It seems like the "referenceKey" field that is being targeted here is actually named s_referenceKey.

To Reproduce

1. In Visual Studio 2019: adding a reference to a duplex service (using the connected services wizard) produces no errors/warnings, but the generated proxy contains invalid annotations: [Microsoft.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.Tools.ServiceModel.Svcutil", "2.0.3-preview3.21351.2")]
2. Running the command using the same tool version: dotnet-svcutil -u "Connected Services\ChemTypesService" --verbosity Debug lead me to:
   [29020.20] Importing metadata ... Error: Object reference not set to an instance of an object.
3. Finally, I got the trace from running the generated SvcutilBootstrapper project.
   " at Microsoft.Tools.ServiceModel.Svcutil.CodeDomHelpers.get_ReferenceKey() in /_/src/dotnet-svcutil/lib/src/CodeDomFixup/CodeDomHelpers.cs:line 29"

Expected behavior
The generated proxy contains no errors (a little message in visual studio in case of a failure would also be nice- I spent half a day looking for some nuget that I thought was missing- e.g. System.CodeDom seemed like a close match- so there had to be something like that..)

Additional context
If I remove the callback interface the same process completes as expected.

[lipchev]

Great- after installing the tool from the locally built nuget (replacing referenceKey with s_referenceKey), I was able to get the correct Reference.cs.

Is there a way to update the package that ships with the IDE? I found it is installed under IDE\Extensions\Microsoft\WCF Connected Service but I don't suppose there is way to set a private nuget source for it somewhere?

[HongGit]

The change is in, waiting to release soon.

[imcarolwang]

The fix has been released to dotnet-svcutil, you can download the latest version of the tool from nuget.org to get the fix. Closing issue.