The type 'System.IEquatable`1<T0>' is defined in an assembly that is not referenced?

Hello, My problem is:
The type ‘System.IEquatable`1’ is defined in an assembly that is not referenced. You must add a reference to assembly ‘netstandard, Version=, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51’.

I give up :(!, I’ve been looking for a solution for 2 weeks now.
I transferred the test project to 3 computers. It works on 2 computers and not on one !. The first is the Studio Community version, the latest version and Windows 10. The 2nd computer is the 60-day Studio version and Windows Server 2016 standard. And on the 3rd computer, which does not work, Studio Community is the latest version and Windows server 2012 Datacenter.

I even did so that I wanted to rewrite the entire project on a new computer to check which activity generates the error.
And after adding some sequences, variables and 2 if after compilation, he gets this error. I haven’t added anything unusual or special. I have no starting point.

All error is:

RemoteException wrapping System.InvalidOperationException: Compilation failures occurred:

The type 'System.IEquatable`1<T0>' is defined in an assembly that is not referenced. You must add a reference to assembly 'netstandard, Version=, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'.

Complete results are contained in the Data property of this exception. Please correct the errors in the source and retry the Load.
at System.Activities.XamlIntegration.ActivityXamlServices.Compile(IDynamicActivity dynamicActivity, LocationReferenceEnvironment environment)
at System.Activities.XamlIntegration.ActivityXamlServices.Load(XamlReader xamlReader, ActivityXamlServicesSettings settings)
at System.Activities.XamlIntegration.ActivityXamlServices.Load(XmlReader xmlReader, ActivityXamlServicesSettings settings)
at System.Activities.XamlIntegration.ActivityXamlServices.Load(Stream stream, ActivityXamlServicesSettings settings)
at UiPath.Executor.WorkflowLoader.LoadWorkflow(String workflowFile)
at UiPath.Executor.WorkflowRuntime.Load(String workflowFile)
at UiPath.Executor.RobotRunner.InitWorkflowApplication()
at UiPath.Executor.RobotRunner.d__86.MoveNext()

I found a bug by accident. And it’s not a bug, but some BUG :frowning:
Resigned, I deleted the activities one by one and after deleting an ordinary assign which had such a form, the project compiled correctly.

Assign has the form:
howMany → type is int32
outReturnMore → type is string

howMany = outReturnMore.Count()

So after erasing it works. This is just some kind of massacre.

How can this be circumvented? how can i fix it? I have similar assignments in several places. And I need them in the project. And I don’t want to make any alpine combinations to get around it.
Should it work unless I’m doing something wrong?

This, It also generates the same error.
dictMap.Values.Sum (x => x.Count ())> 0

howMany = outReturnMore.Count()
but if I change Count() to Length it works.
howMany = outReturnMore.Length

if i change this (Count() to Length)
dictMap.Values.Sum (x => x.Count ())> 0 to dictMap.Values.Sum (x => x.Length)> 0
also generates the same error!

dictMap.Count() > 0

also generates the same error !

I would like to add that only on one computer it does not work and generates an error from 3 computers on which I tested the project !.

Can someone explain it to me?