Start debugging, as soon as you’ve arrived at a breakpoint or used
Debug > Break All, use
Debug > Windows > Modules. You’ll see a list of all the assemblies that are loaded into the process. Locate the one you want to get debug info for. Right-click it and select Symbol Load Information. You’ll get a dialog that lists all the directories where it looked for the .pdb file for the assembly. Verify that list against the actual .pdb location. Make sure it doesn’t find an old one.
Another Way is to disable code optimization
In the IDE, project properties → build → “optimize code”