Azure build:are you missing an assembly reference?

Question

My winforms application builds ok on my machine.

However when the pipeline tries to build it shows

Error CS0234: The type or namespace name 'Dynamic' does not exist in the namespace 'System.Linq' (are you missing an assembly reference?)
Process 'msbuild.exe' exited with code '1'.

The pipeline contains

pool:
   vmImage: 'windows-2019'

variables:
  solution: '**/*.sln'
  buildPlatform: 'Any CPU'
  buildConfiguration: 'Release'
  Major: '2'
  Minor: '0'
  Patch: '0'

steps:
- task: NuGetToolInstaller@0

- task: NuGetCommand@2
  inputs:
    restoreSolution: '$(solution)'

- task: VSBuild@1
  inputs:
    solution: '$(solution)'
    platform: '$(buildPlatform)'
    configuration: '$(buildConfiguration)'

Answer 1

I solved my problem by removing the reference to System.Linq.Dynamic It turned out that I did not need it. Also I found packages.config had an old version which I deleted.