build sql statement with multiple usernames as where conditions.
for example if user input 3 usernames
select tp1, tp2 from table1 where username =@username1 or username =@username2 or username = @username3
you may need to split user input and get each user name like below when you set parameter values
string input ="abc@yahoo.com,def@yahoo.com,efg@yahoo.com";
string[] usernames =input.Split(',');