Error: 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

RR 1

I working in a solution containing a VB and a C# project. It runs well from Visual Studio (2013)development environment and as an executable in the development PC.

When deployed to another PC I keep getting this error:

"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"

This error occurred when an event is trigger from a vb form to display the c# form.

I modified the configuration for the C# project as follow:

<?xml version="1.0" encoding="utf-8"?>
<configuration>

<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0"/> sku=".NETFramework,Version=v4.0"/>
</startup></configuration>

Thanks

1 answer

Karen Payne MVP 35,421 Reputation points

2020-12-27T18:36:46.577+00:00

Hello @RR

You might need to also change sgen.exe.config as per the following Microsoft documentation.
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1 person found this answer helpful.
RR 1 Reputation point

2020-12-27T19:47:49.17+00:00

Thank you for your response .

By Microsoft documentation the sgen.exe.config file need to be modified as follow. I did it, but still doing the same. The application only runs well on the development PC.

<?xml version ="1.0"?>
<configuration>
<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0" />
</startup>
</configuration>

Cheong00 3,476 Reputation points

2020-12-31T04:56:29.77+00:00

You need a little twist in mind to use that article to solve your problem.

The article is for the case that "you fail to build Microsoft .NET Framework 3.5 or lower projects on .NET Framework 4.0 MSBuild or team build where references require Serializer Generator (SGEN)". That's why it tells you to modify "sgen.exe.config".

In your case you need to modify the App.config of the project that loading that mixed assembly instead.

I see the config file you posted in the question have premature end tag "/>" on the line of "supportedRuntime". Try remove that and see if it helps.
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Error: 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

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