If this issue occurs, kindly check web.config in below section
Below section gives the version of particular dll used
after checking this section in web.config, open solution explorer and select reference from the project tree as shown . Solution Explorer->Reference
After expanding reference, find the dll which caused the error. Right click on the dll reference and check for version like shown in the image above.
If both config dll version and referenced dll is different you would get this exception. Make sure both are of same version which would help.