Hi,
Please make sure you select Debug from solution configuration dropdownlist in menu bar.
If the debugger doesn’t load the .pdb file, the Breakpiont cannot be hit. So please make sure that the symbols are loaded by the debugger. We can check if the debugger loads this pdb file by the following steps (Debug->Windows->Modules), and then select your dll module to see if the pdb file is loaded. If the pdb file is not loaded, we can load it manually (Right click the dll model->Select Load Symbols).
You can get more information about debugging by referring to http://blogs.msdn.com/jimgries/pages/visual-studio-debugger-faq.aspx (Section: Breakpoints and other Execution Control).
I look forward to receiving your test results.