Icons shown in the left margin of the IDE during debugging

Question

During debugging, I see these two symbols (shown by green rectangles). Can someone help me understand what this means?

Answer 1

This is used to represent the presence of threads in the current debugger instruction. It allows you to determine which thread is active for the debugger.

For example, when my cursor is in the line Thread.Sleep(10) in this senseless example, I can choose which workflow is of interest to me (and set breakpoints by its process ID):

Here I can see every workflow that is currently active, and that I am now navigating through a workflow with ID 28468. I can also easily specify threads or try to move the cursor to another thread where possible.

Please note that you will only see thread icons if you have enabled "Show streams in source" on the debugger toolbar.