.net - Why does generated IL code start with a Nop?

Question

I was trawling through some of the IL of one of my assemblies (via ILDasm) and I noticed that all of my methods begin with a nop instruction.

Does anyone know why that is?

Answer 1

The assembly was compiled in debug mode. Nop instructions do not do anything (i.e have no side effects), but act as a convenient instruction to place a breakpoint.

Tip

If you need a place for an additional breakpoint for debugging purposes, you can force the inclusion of a Nop in a Debug build by adding a pair of empty braces, e.g.

_grid.PreviewMouseRightButtonDown += (sender, e) =>
{
    _isRightMouseDown = true;

    RowColumnIndex cell = _grid.PointToCellRowColumnIndex(e);
    {} //<------ Adding a Nop allows a breakpoint here.
};