The reason for the problem is that a variable is declared in a header file, but it is defined in two or more. CPP files.

Solution: generally, the compiler will tell you which variable has a problem. You need to locate the variable, and then delete one of the redundant variable definitions

There is also a helpless solution. You can open the project configuration properties connector command line and enter the following string to allow multiple settings:

/ force:multiple   original link: https://blog.csdn.net/qq_ 40222602/article/details/79712192