If you get this error in a Windows Forms project…

Look in your Project–>Properties (ALT+F7) and go to the “Build” tab.
You’ll see the “Platform target”

– If it’s set to “x64”, then make sure you reference the 64-bit Chilkat assembly.
– If it’s set to “x86”, then make sure you reference the 32-bit Chilkat assembly.
– If it’s set to “Any CPU” and the “Prefer 32-bit” checkbox is checked, then your app will run in 32-bit mode and you should reference the 32-bit Chilkat assembly.
– If it’s set to “Any CPU” and the “Prefer 32-bit” checkbox is NOT checked, then your app will run according to the computer (64-bit or 32-bit). It is unlikely you’re developing on a 32-bit Windows computer, so in that case you’d reference the 64-bit Chilkat assembly.