readin txt file

[C# Programming]

Hi friends,

i have a txt file containing email id's like
test.txt
asdf@gmail.com
qwer@gmail.com
zxcv@gmail.com

when user imports test.txt file i want to get the all email id's by comma seperated value... using c#
asdf@gmail.com,qwer@gmail.com,zxcv@gmail.com ....
like this
how can i??
help me plzzz...

icanmakeiteasy