autocompletion of textbox

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C#

i want to develop the for windows application which contains autocompletion feature of the textbox or rich textbox.
eg
p
pooja
poonam
po


if user select pooja and again enters ',' for next selection then it should display autocompletion again like

pooja,p
poonam
pooja
po



if anybody knowing the answer of this problem then please send with code or any link thanks