我们需要用于 SqlCommand 还是仅用于 SqlConnection 和 SqlDataReader 就足够了

do we need using for the SqlCommand or is it enough just for the SqlConnection and SqlDataReader(我们需要用于 SqlCommand 还是仅用于 SqlConnection 和 SqlDataReader 就足够了)

问题描述

我从 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";

      conn.Open();

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

如您所见，这里没有使用 SqlCommand，所以，它需要吗?

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

推荐答案

您需要为您创建的每个实现 IDisposable 的对象使用 using.这包括 SqlCommand 和 SqlConnection.

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

这条规则很少有例外.主要的例外是 WCF 客户端代理.由于设计缺陷，他们的 Dispose 方法有时会抛出异常.如果您在 using 语句中使用了代理，则第二个异常将导致您丢失原始异常.

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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