I was working on a win form project and when changed the .Net Framework version from 2.0 to 4.5 I got 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.

I tried may solutions form the web but nothing work but I solved it by adding this in my startup tag in app.config file

useLegacyV2RuntimeActivationPolicy="true"

and your whole startup will be as folows

</startup>

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