Hi,
replace your sql command with this,
SqlCommand command1 = new SqlCommand("Select price from createproduct where name=" + SelectedItem,con);
Note(Advise):-
Never pass parameter in query like this, it will make your site vulnerable for sql injection.
Insead use it like this,
SqlCommand command1 = new SqlCommand("Select price from createproduct where name=@name",con);
command1.Parameters.AddWithValue("@name", SelectedItem);
Hope it helps you.
Thanks.