In the attached test ptogram I save a List of typed variable data with WriteList and read it back with ReadList.
The returned List size is 4 times the original size.
There are extra commas in the list read back, why?
File.WriteList writes a line for each item, as vb1992 wrote, some of the items span over more than a single line. When you use File.ReadList it takes each line and treats it as a string item.
These methods should not be used with custom types. You should instead use RandomAccessFile.WriteObject / ReadObject. These methods create a binary file that keeps the original structure.
Thank you for your answers and analysis.
I looked a bit further and it seems that the List structure, with a custom Type variable, adds linefeeds after every 3 rd item of the Type variable.