The break point never trigger on submit job even i tried with local account having all dll on my system.
To debug u-sql c# assemblies, you will need to select "Debug" build and start with F5 / Run. If the break point is inside code behind file, it will be handled automatically. If it is in external assemblies, you will need to make sure the correspondent symbol files (*.pdb) can be loaded automatically by VS debugger. You can, for example, either register these symbol files as "WITH ADDITIONAL FILES" during assembly registration, or to follow the guides here: https://learn.microsoft.com/en-us/visualstudio/debugger/specify-symbol-dot-pdb-and-source-files-in-the-visual-studio-debugger?view=vs-2017
You can always check the output log window to see if the correspondent symbols are loaded.
Alternatively, you can add this in the correspondent code to force a break. https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.debugger.break?view=netframework-4.7.2