executereader无可用的连接,已关闭

Question

if (this.comboBox1.SelectedItem.ToString () == "蜀山区")
            {                if (dbcon == null)
                {
                    dbcon = leiku.connection.sqlconnect();                }
                SqlCommand sqlcmd0 = dbcon.CreateCommand();
                sqlcmd0.CommandText = leiku.connection.getshushandiqu();
                SqlDataReader sqlD = sqlcmd0.ExecuteReader();
                if (sqlD.Read())
                {
                    this.listBox1.Items.Clear();
                    this.listBox1.Items.Add(sqlD.GetString(0).Trim());
                    
                }
                //sqlcmd.Dispose();
                //sqlD.Close();
            }
            else if (this.comboBox1.SelectedItem.ToString () == "包河区")
            {
                SqlCommand sqlcmd1 = dbcon.CreateCommand();
                sqlcmd1.CommandText = leiku.connection.getbaohediqu();
                MessageBox.Show(sqlcmd1.CommandText.ToString());
                SqlDataReader sqlB = sqlcmd1.ExecuteReader();
                if (sqlB.Read())
                {
                    this.listBox1.Items.Clear();
                    this.listBox1.Items.Add(sqlB.GetString(0).Trim());
                    
                }
                //sqlcmd.Dispose();
                //sqlB.Close();
            }
为什么不加else if就行了.是不是前面的executereader没有释放啊.

Answer 1

你加了Else if 后,dbcon就没有被初始化或连接,代码明显有问题

Answer 2

报错的原因是sqlcmd1对应的链接没有open,而是close了

Answer 3

不对啊.
你加了Else if 后,dbcon就没有被初始化或连接,代码明显有问题
有连接啊.
这个问题怎么解决啊!

Answer 4

if (dbcon == null)
                {
                    dbcon = leiku.connection.sqlconnect();                }
zhge?

Answer 5

private static SqlConnection sqlcon = null;
        
        public static SqlConnection sqlconnect()
        {
            if(sqlcon == null)
            {
                sqlcon = new SqlConnection(con);
                sqlcon.Open();
            }
            return sqlcon;
        }
这个数据库连接啊.