The using statement forces the connection to close, regardless of whether there is an error : using « ADO.net Database « ASP.NET Tutorial

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using statement also disposes of the Connection object. 
If you need to reuse the Connection, then you need to reinitialize it.



SqlConnection con = new SqlConnection("Data Source=localhost;Integrated Security=True;Initial Catalog=Pubs");
SqlCommand cmd = new SqlCommand("INSERT Titles (Title) VALUES ('Some Title')", con);
using (con)
{
  con.Open();
  cmd.ExecuteNonQuery();
}