How to determinate a SqlConnection is open or not

I use a common connection cnn;
If the conn is opened, if I open it again, it will through a exception
How can I determinate a SqlConnection is open or not before I open it?
conn.State
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"ad" <ad@.wfes.tcc.edu.tw> wrote in message
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>I use a common connection cnn;
> If the conn is opened, if I open it again, it will through a exception
> How can I determinate a SqlConnection is open or not before I open it?
>
>