query string Null exception RSS

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  Hunain Hafee...

  Member

  238 Points

  639 Posts

  query string Null exception

  Nov 07, 2012 08:08 PM|LINK

  i am using query string to send pagename in to another page, if pagename is equal to intended page then it would be redirected to mentioned url else if pagename (querystring) is null then page would be redirected to some other page , so first condition is working but not the second one, when query string is not set, i get error, 

  Object reference not set to an instance of an object.
  
  Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
  
  Exception Details: System.NullReferenceException: Object reference not set to an instance of an object. Source Error: Line 23: protected void btnsubmit_Click(object sender, EventArgs e) Line 24: { Line 25: String pageName = Request.QueryString["pageName"].ToString(); 

  ASPX code :

  using System;
  using System.Collections;
  using System.Configuration;
  using System.Data;
  using System.Linq;
  using System.Web;
  using System.Web.Security;
  using System.Web.UI;
  using System.Web.UI.HtmlControls;
  using System.Web.UI.WebControls;
  using System.Web.UI.WebControls.WebParts;
  using System.Xml.Linq;
  using System.Data.SqlClient;
  
  public partial class loginApplicant : System.Web.UI.Page
  {
  protected void Page_Load(object sender, EventArgs e)
  {
  
  }
  protected void btnsubmit_Click(object sender, EventArgs e)
  { 
  String pageName = Request.QueryString["pageName"].ToString();
  int advId = int.Parse(Request.QueryString["advId"]);
  String hashedPwd = FormsAuthentication.HashPasswordForStoringInConfigFile(txtboxPassword.Text, "SHA1");
  //Response.Write(hashedPwd);
  String conString = "Data Source=COSANOSTRA;Initial Catalog=Waleed_orsfinal;Integrated Security=True";
  SqlConnection con = new SqlConnection(conString);
  String query = "select email,password from tblUser where email='" + txtboxUserEmail.Text + "' and password= '" + hashedPwd + "' ";
  SqlCommand com = new SqlCommand(query, con);
  
  try
  {
  con.Open();
  SqlDataReader dr = com.ExecuteReader();
  
  if (dr.Read() == true && pageName == "page_applyForJob")
  {
  Session["applicantSession"] = txtboxUserEmail.Text;
  Response.Redirect("applyForJob.aspx?advId=" + advId);
  }
  
  else if (dr.Read() == true && pageName== null ) { Session["applicantSession"] = txtboxUserEmail.Text; Response.Redirect("~/showAdvertsiement.aspx"); }
  else
  {
  
  Response.Write("Wrong Combination Of Email and Password");
  }
  }
  catch (Exception ex)
  {
  
  Response.Write("error" + ex.Message);
  
  
  }
  finally
  {
  con.Close();
  }
  }
  }
  

  
  
  

  help please, in situation of null value i want it to redirect to mentioned page

  Hunain Hafeez
  • Edited by Hunain Hafeez on Nov 07, 2012 08:10 PM
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  inquisitive_...

  Contributor

  3421 Points

  575 Posts

  Re: query string Null exception

  Nov 07, 2012 08:46 PM|LINK

  Check for null reference

  String pageName = Request.QueryString["pageName"] ==  null ? null : Request.QueryString["pageName"].ToString();
  int advId = Request.QueryString["advId"] == null ? 0 : int.Parse(Request.QueryString["advId"]);

  
  
  

  *** If this post helps you, then Mark this post as Answer ***
  
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• • Reply
  

  Hunain Hafee...

  Member

  238 Points

  639 Posts

  Re: query string Null exception

  Nov 07, 2012 08:53 PM|LINK

  thanks but little problem occurred but Thank God, that error disappeared,

  now problem is that only else block is executed when i put pageName equals to null + putting ur code in my code,

  but without pagename equal to null, it logins successfully, y ? 

  now my code is this :

  using System;
  using System.Collections;
  using System.Configuration;
  using System.Data;
  using System.Linq;
  using System.Web;
  using System.Web.Security;
  using System.Web.UI;
  using System.Web.UI.HtmlControls;
  using System.Web.UI.WebControls;
  using System.Web.UI.WebControls.WebParts;
  using System.Xml.Linq;
  using System.Data.SqlClient;
  
  public partial class loginApplicant : System.Web.UI.Page
  {
      protected void Page_Load(object sender, EventArgs e)
      {
          
          
  
      }
      protected void btnsubmit_Click(object sender, EventArgs e)
      {
         // String pageName = Request.QueryString["pageName"].ToString();
         // int advId = int.Parse(Request.QueryString["advId"]);
          String pageName = Request.QueryString["pageName"] ==  null ? null : Request.QueryString["pageName"].ToString();
          int advId = Request.QueryString["advId"] == null ? 0 : int.Parse(Request.QueryString["advId"]);
          String hashedPwd = FormsAuthentication.HashPasswordForStoringInConfigFile(txtboxPassword.Text, "SHA1");
          //Response.Write(hashedPwd);
          String conString = "Data Source=COSANOSTRA;Initial Catalog=Waleed_orsfinal;Integrated Security=True";
          SqlConnection con = new SqlConnection(conString);
          String query = "select email,password from tblUser where email='" + txtboxUserEmail.Text + "' and password= '" + hashedPwd + "' ";
          SqlCommand com = new SqlCommand(query, con);
  
          try
          {
              con.Open();
              SqlDataReader dr = com.ExecuteReader();
  
              if (dr.Read() == true && pageName == "page_applyForJob")
              {
                   Session["applicantSession"] = txtboxUserEmail.Text;
                   Response.Redirect("applyForJob.aspx?advId=" + advId);
               }
  
              else if (dr.Read() == true && pageName== null)
              {
                  
                  Session["applicantSession"] = txtboxUserEmail.Text;
                  Response.Redirect("~/showAdvertsiement.aspx");
              }
              else { Response.Write("Wrong Combination Of Email and Password"); }
          }
          catch (Exception ex)
          {
  
              Response.Write("error" + ex.Message);
  
  
          }
          finally
          {
              con.Close();
          }
      }
  }

  chek bold section, it is executed when i place pagename= null, and even no parameter is passing to it

  Hunain Hafeez
  • Edited by Hunain Hafeez on Nov 07, 2012 09:13 PM
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  ramiramilu

  All-Star

  98023 Points

  14516 Posts

  Re: query string Null exception

  Nov 08, 2012 07:46 AM|LINK

  instead of equating it to null, equat it to string.empty, then check for pageName == string.empty in the Else If condition....also make sure your dr.Read() is true or else it will not enter into that condition...

  i would rather say use String.IsNullOrWhiteSpace to check whether string is empty or not...that is more easier way...http://msdn.microsoft.com/en-us/library/system.string.isnullorwhitespace.aspx

  Thanks,

  Website
  JumpStart
  • Marked as answer by Hunain Hafeez on Nov 10, 2012 06:46 PM
• • Reply
  

  UjjwalMeshra...

  Participant

  1179 Points

  293 Posts

  Re: query string Null exception

  Nov 08, 2012 08:07 AM|LINK

  hi, first check for dr.read() then check for pagename in two different if statements. like below

  if (dr.Read() == true)
  {
  
       if (!string.IsNullOrEmpty(pageName))
       {
  	 if(pageName == "page_applyForJob")
              {
                   Session["applicantSession"] = txtboxUserEmail.Text;
                   Response.Redirect("applyForJob.aspx?advId=" + advId);
               }
       }
  
       else
       {
                  
           Session["applicantSession"] = txtboxUserEmail.Text;
           Response.Redirect("~/showAdvertsiement.aspx");
       }
  }
  else { Response.Write("Wrong Combination Of Email and Password"); }

  hope this helps

  When a eye with Vision and a heart with passion achieves his dream people call him genius.
  
  Regards
  • Marked as answer by Hunain Hafeez on Nov 10, 2012 06:46 PM
• • Reply
  

  Hunain Hafee...

  Member

  238 Points

  639 Posts

  Re: query string Null exception

  Nov 09, 2012 06:06 PM|LINK

  ok thanks 

  Hunain Hafeez
  • Edited by Hunain Hafeez on Nov 09, 2012 06:07 PM
  • Edited by Hunain Hafeez on Nov 10, 2012 06:46 PM