c# 方法引用问题!!

Question

        public void DBconn()
        {
            string USERID, PASSWORD, DATASOURCE;
            XmlTextReader reader = new XmlTextReader(".\\dataconfig.xml");
            DataSet myDs = new DataSet();
            myDs.ReadXml(reader);
            DataRow myDataRow = myDs.Tables[0].Rows[0];
            USERID = myDataRow["userid"].ToString();
            PASSWORD = myDataRow["password"].ToString();
            DATASOURCE = myDataRow["DataSource"].ToString();
            string sqlString = "Data Source=" + DATASOURCE + ";user id=" + USERID + ";password =" + PASSWORD + "";
            OracleConnection con = new OracleConnection(sqlString);
            //myDs.Dispose();
            con.Open();
            
        
        }
        private void button1_Click(object sender, EventArgs e)
        {
            if (names.Text.Trim() == "")
            {
                MessageBox.Show("用户名不能为空！", "提示信息");
                names.Focus();
                return;
            }
            if (pwd.Text.Trim() == "")
            {
                MessageBox.Show("密码不能为空！", "提示信息");
                pwd.Focus();
                return;
            }
            int i = 0;           
           
            login con = new login();
            con.DBconn();
            OracleConnection conn = new OracleConnection();
            conn.Open(); //提示报错 ConnectionString 属性尚未初始化
            
            
                        
            {
                string password1 = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(pwd.Text, "MD5");
                string sql = "select count(*) from test  where test1='" + names.Text.Trim() + "' and test2='" + password1 + "'";
                
  
                using (OracleCommand cmd = conn.CreateCommand())
                {
                  cmd.CommandText = sql;                   
                  i = (int)Convert.ToInt32(cmd.ExecuteScalar());
                }
            }
            if (i > 0)
            {
                bl = true;                        
                this.Close();
                MainForm MF = new MainForm();
                MF.Show();
                conn.Close();               
            }
            else
            {
                MessageBox.Show("用户名或密码错误！请重新登陆！", "提示信息");
            }

Answer 1

OracleConnection conn = new OracleConnection(); 
            conn.Open(); //提示报错 ConnectionString 属性尚未初始化 很明显ConnectionString 属性没初始化啊
改成下面这样。
OracleConnection conn = new OracleConnection(sqlString); 
conn.Open();

Answer 2

using(OracleConnection conn = new OracleConnection(""))
{ 
  conn.Open();
} 

Answer 3

 OracleConnection conn = new OracleConnection(); 
            conn.Open(); //提示报错 ConnectionString 属性尚未初始化 这里面的连接字符串呢？另外conn不能只open，要记得close啊

Answer 4

按照你的改完后下面语句又出现新的报错 login con = new login();
            con.DBconn();
            using (OracleConnection conn = new OracleConnection(""))
            {
                conn.Open();
            }
            
             string password1 = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(pwd.Text, "MD5");
             string sql = "select count(*) from test where test1='" + names.Text.Trim() + "' and test2='" + password1 + "'";
             using (OracleCommand cmd = conn.CreateCommand()) //当前上下文中不存在名称“conn”
                {
                  cmd.CommandText = sql;                   
                  i = (int)Convert.ToInt32(cmd.ExecuteScalar());
                }
            
            if (i > 0)
            {
                bl = true;                        
                this.Close();
                MainForm MF = new MainForm();
                MF.Show();
                conn.Close();////当前上下文中不存在名称               
            }
            else
            {
                MessageBox.Show("用户名或密码错误！请重新登陆！", "提示信息");
            }