How do I put a breakpoint on the left and get the line number

[i-LinX]

How do I put a breakpoint on the left and get the line number

[siegfriedpammer]

There is a working implementation of breakpoints in SharpDevelop. A starting point would be the implementation of the bookmarks margin: https://github.com/icsharpcode/SharpDevelop/blob/master/src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/IconBarMargin.cs

Hope this helps!