do we need using for the SqlCommand or is it enough just for the SqlConnection and SqlDataReader

i took this code from msdn

string connString = "Data Source=localhost;Integrated Security=SSPI;Initial Catalog=Northwind;";

    using (SqlConnection conn = new SqlConnection(connString))
    {
      SqlCommand cmd = conn.CreateCommand();
      cmd.CommandText = "SELECT CustomerId, CompanyName FROM Customers";

      co开发者_运维技巧nn.Open();

      using (SqlDataReader dr = cmd.ExecuteReader())
      {
        while (dr.Read())
          Console.WriteLine("{0}\t{1}", dr.GetString(0), dr.GetString(1));
      }
    }

as you can see there is no using for the SqlCommand here, so, does it needs to be ?

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You need a using for every object you create that implements IDisposable. That includes the SqlCommand and the SqlConnection.

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There are very few exceptions to this rule. The main exception is WCF client proxies. Due to a design flaw, their Dispose method can sometimes throw an exception. If you used the proxy in a using statement, this second exception would cause you to lose the original exception.

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You don't NEED to use a using statement, but it is good practice and you SHOULD use it. It allows objects using IDisposable to be disposed of automatically.

http://msdn.microsoft.com/en-us/library/yh598w02(VS.80).aspx

Edited to add link and remove inaccurate statement because @John Saunders is right.