Could not load file or assembly crdb_adoplus.dll

Use only

<startup useLegacyV2RuntimeActivationPolicy="true">
</startup>

It works for all frameworks!

Please use this code. It may be helpful for you.

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

This is slightly different than you. For more details visit this link Crystal Report Viewer

Change the first line to work successfully

After you open a file "App.config" from Solution Explorer

Previous:

<startup> 

<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/></startup>

Current:

<startup useLegacyV2RuntimeActivationPolicy="true">

<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/></startup>

This stuff basically happens, if you have correct setup of SBO (I wish you so:)), that between different components of your SBO SDK there are assemblies with different .NET version. Check if you have some old version of SAP BO SDK installed on your machine too. Hope this helps.