我已尽力解决它，但我做不到。请帮助 me.The 连接未关闭。连接的当前状态是打开的

Question

我正在尝试在我的数据库中插入日期（从和到），试试这个代码，但它总是向我显示这个错误：

The connection was not closed. The connection's current state is open.

当我删除中间的 con.Open() 时，它抛出异常：

ExecuteReader: Connection property has not been initialized.

private void btnDiff_Click(object sender, EventArgs e)
    {
        DateTime oldDate = DateTime.Parse(txtFirstDate.Text);
        DateTime fromdate = oldDate;
        DateTime todate = oldDate;

        SqlCommand cmd1 = new SqlCommand("SELECT [Topic_ID] FROM [CourseDB].[dbo].[Topic]", con);
        con.Open();
        SqlDataReader reader = cmd1.ExecuteReader();
            while (reader.Read())
            {
               string column = reader["Topic_ID"].ToString();
               int a = Convert.ToInt32(reader["Topic_ID"]);

               fromdate = todate.AddDays(0);
               todate = fromdate.AddDays(7);

                SqlCommand cmd = new SqlCommand();
                con.Open();
                SqlDataReader r = cmd.ExecuteReader();
                while (r.Read())
                {
                    con.CreateCommand();
                    cmd.CommandType = CommandType.Text;
                    cmd.CommandText = "UPDATE [CourseDB].[dbo].[Topic] SET [From_Date]='" + fromdate.ToString() + "', [To_Date]='" + todate.ToString() + "' WHERE [Topic_ID]='" + a + "'";
                    cmd.ExecuteNonQuery();
                    MessageBox.Show("Dates Inserted");
                }
                r.Close();
                con.Close();
             }
        reader.Close();
        con.Close();
     }

Answer 1

我不明白你用下面的代码在做什么。

SqlCommand cmd = new SqlCommand();
con.Open();
SqlDataReader r = cmd.ExecuteReader();

cmd要执行什么命令。没有指定任何命令文本。

根据我的说法，您应该建立单独的连接 class，这有助于您正确维护代码。

public class AppConnection
{
    public string ConnectionString
    {
        get { return ConfigurationManager.ConnectionStrings["WebConfigConnectionStringName"].ConnectionString; }
    }

    public SqlConnection MakeConnection()
    {
        SqlConnection newConnection = new SqlConnection(this.ConnectionString);
        if (newConnection.State == ConnectionState.Closed)
        {
            newConnection.Open();
        }

        return newConnection;
    }

    public SqlDataReader ExecCommand(string commandText, CommandType commandType, ref SqlConnection appConnection)
    {
        SqlDataReader reader;

        using (SqlCommand dbCommand = new SqlCommand())
        {
            dbCommand.CommandText = commandText;
            dbCommand.CommandType = commandType;
            dbCommand.Connection = appConnection;

            reader = dbCommand.ExecuteReader();
        }

        return reader;
    }
}

按钮点击事件可能是这样的:-

private void btnDiff_Click(object sender, EventArgs e)
    {
        DateTime oldDate = DateTime.Parse(txtFirstDate.Text);
        DateTime fromdate = oldDate;
        DateTime todate = oldDate;

        AppConnection appConnection = new AppConnection();
        SqlConnection con = appConnection.MakeConnection();

        SqlDataReader readerTopics = appConnection.ExecCommand("SELECT [Topic_ID] FROM [CourseDB].[dbo].[Topic]", CommandType.Text, ref con);
        while (readerTopics.Read())
        {
            string column = readerTopics["Topic_ID"].ToString();
            int a = Convert.ToInt32(readerTopics["Topic_ID"]);

            fromdate = todate.AddDays(0);
            todate = fromdate.AddDays(7);

            using (SqlCommand updateCommand = new SqlCommand())
            {
                updateCommand.CommandText = "UPDATE [CourseDB].[dbo].[Topic] SET [From_Date]='" + fromdate.ToString() + "', [To_Date]='" + todate.ToString() + "' WHERE [Topic_ID]='" + a + "'";
                updateCommand.Connection = con;
                updateCommand.CommandType = CommandType.Text;
                updateCommand.ExecuteNonQuery();
            }
        }
    }

Answer 2

我就是这么做的，我的问题就解决了:)

DateTime oldDate = DateTime.Parse(txtFirstDate.Text);
            DateTime fromdate = oldDate;
            DateTime todate = oldDate;

            SqlCommand cmd1 = new SqlCommand("SELECT [Topic_ID] FROM [CourseDB].[dbo].[Topic]", con);
            con.Open();

            DataTable dt = new DataTable();
            SqlDataAdapter adapter = new SqlDataAdapter(cmd1);
            adapter.Fill(dt);

            foreach (DataRow row in dt.Rows)
            {
                string column = row["Topic_ID"].ToString();
                int a = Convert.ToInt32(row["Topic_ID"]);

                fromdate = todate.AddDays(0);
                todate = fromdate.AddDays(7);

                SqlCommand cmd = new SqlCommand();
                cmd.Connection = con;
                cmd.CommandType = CommandType.Text;
                cmd.CommandText = "UPDATE [CourseDB].[dbo].[Topic] SET [From_Date]='" + fromdate.ToString() + "', [To_Date]='" + todate.ToString() + "' WHERE [Topic_ID]='" + a + "'";
                cmd.ExecuteScalar();
                this.topicTableAdapter.Fill(this.courseDataSet.Topic);

我已尽力解决它，但我做不到。请帮助 me.The 连接未关闭。连接的当前状态是打开的

I tried enough to solve it, but i can't. Please Help me.The connection was not closed. The connection's current state is open

sql-server-2008

c#-4.0