I know I need to use the null-coalescing assignment operator but can't figure out how to apply it to this statememt

Question

Here is what I am trying to Coalesce "while ((line = reader.ReadLine()) != null)" and I have tried many things and finally had to admit, it is difficult because I really don't fully understand how to apply it to many different situations. Can somebody help?

I deleted all my attempts, so code is back to getting CS8600 error and I don't remember all the fails I had.