c# - ExecuteNonQuery 需要一个打开且可用的连接。连接的当前状态是关闭的

Question

ExecuteNonQuery 需要一个打开且可用的连接。连接的当前状态为关闭。

我在这里做错了什么？我假设您可以重用该连接？

感谢您的帮助!

using (SqlConnection cn = new SqlConnection(ConfigurationManager.ConnectionStrings["LocalSqlServer"].ToString()))
{
    cn.Open();

    // If we are reverting to an old type
    if (pageAction == "revert")
    {
        debug.Text = "FLAG 1";

        // Get the revert ID
        int revertingID = int.Parse(Request.QueryString["revID"]);
        bool rowsReturned = false;

        debug.Text = "FLAG 2 - " + revertingID.ToString();

        // Set all to 0
        using (SqlCommand cmd = new SqlCommand("SELECT ID FROM tblSiteSettings WHERE ID = " + revertingID, cn))
        {
            // If it exists
            SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            if (rdr.Read())
            {
                rowsReturned = true;
            }
            rdr.Close();
        }

        debug.Text = "FLAG 3 - " + rowsReturned.ToString();

        // Set new active and reset others
        if (rowsReturned == true)
        {
            using (SqlCommand cmd = new SqlCommand("UPDATE tblSiteSettings SET isActive = 1 WHERE ID = " + revertingID, cn))
            {
                cmd.ExecuteNonQuery();
            }
            using (SqlCommand cmd = new SqlCommand("UPDATE tblSiteSettings SET isActive = 0 WHERE ID <> " + revertingID, cn))
            {
                cmd.ExecuteNonQuery();
            }
        }
        //debug.Text = "FLAG 4 - ";
    }

Answer 1

你的问题是:

SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);

如果您想在“摆脱”它之前再次使用该连接，您应该只调用 cmd.ExecuteReader()'。如果您想了解 CommandBehaviour.CloseConnection 部分的作用/含义，请参阅 SqlCommand.ExecuteReader 的文档是一个不错的选择。还有文档告诉您 CommandBehaviour enumeration 的所有可能值是什么是。本质上，CommandBehaviour.CloseConnection 执行以下操作:

When the command is executed, the associated Connection object is closed when the associated DataReader object is closed.

如果您没有特别需要指定 CommandBehaviour，则可以指定 CommandBehaviour.Default，或者根本不指定。 CommandBehaviour.Default 是:

The query may return multiple result sets. Execution of the query may affect the database state. Default sets no CommandBehavior flags, so calling ExecuteReader(CommandBehavior.Default) is functionally equivalent to calling ExecuteReader().