You could try wrapping your strings in quotations:
IEnumerable<string> query =
(
from row in dt.AsEnumerable()
select row.Field<string>("ID")
+ ", \""
+ row.Field<string>("Text")
+ "\""
).Distinct();
Also, since you are including the comma as a part of your selection query, I don't think you will need to split the string before writing it out.