问题描述

我在这里使用遗留代码，并且有许多 SqlDataReader 实例从未关闭或处置.连接已关闭，但我不确定是否需要手动管理阅读器.

I'm working with legacy code here and there are many instances of SqlDataReader that are never closed or disposed. The connection is closed but, I am not sure if it is necessary to manage the reader manually.

这会导致性能下降吗?

推荐答案

尽量避免这样使用阅读器:

Try to avoid using readers like this:

SqlConnection connection = new SqlConnection("connection string");
SqlCommand cmd = new SqlCommand("SELECT * FROM SomeTable", connection);
SqlDataReader reader = cmd.ExecuteReader();
connection.Open();
if (reader != null)
{
      while (reader.Read())
      {
              //do something
      }
}
reader.Close(); // <- too easy to forget
reader.Dispose(); // <- too easy to forget
connection.Close(); // <- too easy to forget

相反，将它们包装在 using 语句中:

Instead, wrap them in using statements:

using(SqlConnection connection = new SqlConnection("connection string"))
{

    connection.Open();

    using(SqlCommand cmd = new SqlCommand("SELECT * FROM SomeTable", connection))
    {
        using (SqlDataReader reader = cmd.ExecuteReader())
        {
            if (reader != null)
            {
                while (reader.Read())
                {
                    //do something
                }
            }
        } // reader closed and disposed up here

    } // command disposed here

} //connection closed and disposed here

using 语句将确保正确处理对象并释放资源.

The using statement will ensure correct disposal of the object and freeing of resources.

如果您忘记了，那么您将把清理工作留给垃圾收集器，这可能需要一段时间.

If you forget then you are leaving the cleaning up to the garbage collector, which could take a while.

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