Probably, you have to set the Platform Target in the Build tab.
If your application is for 32-bit system, set it it x86 and use the ActualMap assemblies from the BIN32 folder.
For 64-bit systems use x64 and the assemblies from the BIN64 folder.
Visual Studio is 32-bit and only the assemblies from the BIN32 folder can be added to the Toolbox. If you plan to deploy your application as 64-bit, you will need to replace the 32-bit ActualMap assemblies with 64-bit before deployment.