Had tried to launch SignalR client (.NET Framework 4.5 target) on my Pi 3 with Mono on Raspbian. But it's not working because SignalR's throws a System.InvalidProgramException - something wrong with Cryptography.X509Certificates.X509CertificateCollection constructor...

Unhandled Exception: System.AggregateException: ---> System.InvalidProgramException: Invalid IL code in System.Security.Cryptography.X509Certificates.X509CertificateCollection:.ctor (): method body is empty.

Is there anyone here who has an idea how to fix it?

  • Could you get your Mono version and edit that into your post? Thanks.
    – Aurora0001
    Commented Sep 10, 2017 at 12:31

1 Answer 1


Yep, @Aurora0001 you're right, thanks!

So, I did only sudo apt-get install mono-complete which installed the Mono 3.2.8 instead the latest version.

I forgot add the Mono repository to my system:

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
echo "deb http://download.mono-project.com/repo/debian raspbianjessie main" | sudo tee /etc/apt/sources.list.d/mono-official.list
sudo apt-get update

And after that install the Mono:

sudo apt-get install mono-complete

And the Mono 5.2.0 was installed!


  • Note: This installed Version for me, on Raspbian Jessie Commented Apr 26, 2018 at 11:36
  • 1
    @TheColonel26 yep, cause in Sept '17 the latest version was 5.2.0. You can see latest stable version here mono-project.com/download
    – MihailPw
    Commented Apr 27, 2018 at 11:58

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