PDB Files (C# and Visual Basic)
A program database (PDB) file holds debugging and project state information that allows incremental linking of a debug configuration of your program. A PDB file is created when you build with /debug (Visual Basic/C#). You can build Visual Basic and Visual C# applications with /debug:full or /debug:pdbonly. Building with /debug:full generates debuggable code. Building with /debug:pdbonly generates PDBs but does not generate the DebuggableAttribute that tells the JIT compiler that debug information is available. Use /debug:pdbonly if you want to generate PDBs for a release build that you do not want to be debuggable.
The Visual Studio debugger uses the path to the PDB in the EXE or DLL file to find the project.pdb file. If the debugger cannot find the PDB file at that location, or if the path is invalid, for example, if the project was moved to another computer, the debugger searches the path containing the EXE followed by the symbol paths specified in the Options dialog box. This path is generally the Debugging folder in the Symbols node. The debugger will not load a PDB that does not match the binary being debugged.