eReader requires an open and available Connection. The connection's current state is closed

eReader requires an open and available Connection. The connection's
current state is closed

i have C# windows form application form with textbox and richtextbox. I
have to type word in textbox and search meaning of that word in sql
database.But when i accessed one word's meaning from database and try to
access another word's meaning by typing on text box and click on search
botton, it shows error message "ExecuteReader requires an open and
available Connection. The connection's current state is closed.". Anyone
can help me, how to reopen connection at same run time.