运行程序时出现了 ORA-12154: TNS: 无法解析指定的连接标识符解决方法

运行程序时出现了 ORA-12154: TNS: 无法解析指定的连接标识符
源代码如下:
using System;
using System.Collections;
using System.ComponentModel;
using System.Configuration;
using System.Data;
using System.Data.OracleClient;
using System.Drawing;
using System.Web;
using System.Web.Security;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text;

public partial class _Default : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
  string sConfirmCode;
  this.Title = "欢迎光临XXXXXXX中心";


  if (!IsPostBack)
  {
  if (Session["UserID"] == null)
  {
  LabelWelcome.Text = "欢迎光临，请先登陆";
  }

  //增加了创建验证码得代码 2007－3－1 congcong
  sConfirmCode = GetConfirmCode(5);
  Session["ConfirmCode"] = sConfirmCode;
  Image1.ImageUrl = "ImageConfirmCode.aspx";
  // 增加代码结束 2007－3－1 congcong
  }
  }
  protected void ButtonLogin_Click(object sender, EventArgs e)
  {
  string sUserID, sPassword, sUserName, sUserLvl, sCompany;

  //增加了对于验证码得判断 2007－3－1 congcong
  string sConfirmCode,sSessionConfirmCode;
  sConfirmCode = TextBoxConfirmCode.Text;
  sSessionConfirmCode = Session["ConfirmCode"].ToString();
  if (sConfirmCode != sSessionConfirmCode)
  {
  Response.Redirect("错误报告.aspx?ErrorCode=验证码输入错误！请返回，重新输入");
  }

  // 增加代码结束 2007－3－1 congcong

  sUserID = TextBoxUserID.Text;
  sPassword = TextBoxUserPassword.Text;

  LabelWelcome.Text = sUserID;
  string sConnectionString, sSelectCommand;

  sConnectionString = ConfigurationManager.ConnectionStrings["OraConnectionString"].ConnectionString;
  OracleConnection MyConnection = new System.Data.OracleClient.OracleConnection(sConnectionString);

  sSelectCommand = "scott.P_CHECK_USER_PASSWORD";
  OracleCommand MyCommand = new OracleCommand();
  MyCommand.Connection = MyConnection;
  MyCommand.CommandText = sSelectCommand;
  MyCommand.CommandType = CommandType.StoredProcedure;

  MyCommand.Parameters.Add("vUserID", OracleType.VarChar).Value = sUserID;
  MyCommand.Parameters.Add("vUserPassword", OracleType.VarChar).Value = sPassword;
  MyCommand.Parameters.Add("vUserlvl", OracleType.VarChar, 1).Direction = ParameterDirection.Output;
  MyCommand.Parameters.Add("CountUser", OracleType.Number).Direction = ParameterDirection.Output;
  MyCommand.Parameters.Add("vUserName", OracleType.VarChar, 20).Direction = ParameterDirection.Output;
  MyCommand.Parameters.Add("vCompany", OracleType.VarChar, 20).Direction = ParameterDirection.Output;

  MyCommand.Connection.Open();
  MyCommand.ExecuteNonQuery();

  if (Convert.ToInt32(MyCommand.Parameters["CountUser"].Value) == 0)
  {
  Response.Redirect("错误报告.aspx?ErrorCode=5");
  return;
  }
  else if (MyCommand.Parameters["CountUser"].Value == null)
  {
  Response.Redirect("错误报告.aspx?ErrorCode=6");

  return;
  }
  else if (Convert.ToInt32(MyCommand.Parameters["CountUser"].Value) != 1)
  {
  Response.Redirect("错误报告.aspx?ErrorCode=不可预知的错误");
  return;
  }

  sUserName = MyCommand.Parameters["vUserName"].Value.ToString();
  sCompany = MyCommand.Parameters["vCompany"].Value.ToString();
  sUserLvl = MyCommand.Parameters["vUserlvl"].Value.ToString();
  LabelWelcome.Text = "欢迎你光临西南物流网上查询系统：" + sUserName;

  Session["UserID"] = sUserID;
  Session["UserName"] = sUserName;
  Session["UserLvl"] = sUserLvl;
  Session["Company"] = sCompany;

  string sSelectCommand1;//qrj edit at 2007.10.08
  //增加对于用户冻结状态的判断

  sSelectCommand1 = "select userstatu from scott.netusersearch where userid = :userid";
  OracleCommand MyCommand1 = new OracleCommand();
  MyCommand1.Connection = MyConnection;
  MyCommand1.CommandText = sSelectCommand1;
  MyCommand1.CommandType = CommandType.Text;
  MyCommand1.Parameters.Add(":userid", OracleType.VarChar).Value = sUserID;

  MyCommand1.Connection.Open();

  OracleDataReader odr;

  odr = MyCommand1.ExecuteReader();

  string sStatu;
  if (odr.Read())
  {
  sStatu = odr[0].ToString();
  }
  else
  {
  Response.Redirect("错误报告.aspx?ErrorCode=不存在输入的用户ID");
  return;
  }
  odr.Close();

  if (sStatu == "0")
  {
  Response.Redirect("错误报告.aspx?ErrorCode=输入的用户ID的用户已经处于冻结状态，需要解除冻结才能登录！");
  return;
  }

  MyCommand.Connection.Close();

  Response.Redirect("load.aspx");
  }

  protected string GetConfirmCode(int VcodeNum)
  {
  string Vchar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
  string[] VcArray = Vchar.Split(new Char[] { ',' });
  string VNum = "";
  int temp = -1;

  Random rand = new Random();

  for (int i = 1; i < VcodeNum + 1; i++)
  {
  if (temp != -1)
  {
  rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
  }

  int t = rand.Next(35);

  temp = t;
  VNum += VcArray[t];
  }
  return VNum;
  }
}
报错位置如下:
  MyCommand.Connection.Open();
大家帮帮吧,谢谢啦

[解决办法]
http://www.cnblogs.com/davidullua/articles/180792.html
[解决办法]
配置一下listener.ora和tnsnames.ora文件。也可以直接用Net Manager
配置。
如果再不行的话，可能是web.config 里的OraConnectionString连接语句錯了。
[解决办法]
连接字符串写的不对，照下面这个写试试
<add key="OraConnectionString" value="user id=abc;data source=servername;password=123"></add>
abc是用户名
123是口令
servername是服务名