While Resharper has many cool features it has a large impact in CPU and I/O usage and can be very complicated to use. It is also only available under commercial licensing unless you qualify for a few very specific free use licenses.
Try CodeMaid. It is free for commercial use and has a much lower performance overhead. I find it easy to use and it is very good for alphabetizing methods.
To sort your file, open the file via solution explorer:
- Right click the open file
- Code Maid menu (likely near the top of the right click menu)
- Click
Reorganize Active Document
Alternatively, using the default CodeMaid hotkeys CTRL+M,Z to sort your active file.