This compilation error may be caused by using conflicting assemblies (e.g., it could occur if some assemblies of an older version were not deleted).
Try to do the following steps:
- uninstall dotConnect for MySQL;
- remove all Devart.* and policy.*.Devart.* files from the GAC;
- clear the Program Files\Devart\dotConnect and Program Files\Common Files\Devart\dotConnect folders;
- clear the bin folder of your application;
- reinstall dotConnect for MySQL.