data reader problem RSS

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  rajeevinime

  Member

  406 Points

  229 Posts

  data reader problem

  Sep 19, 2010 05:40 AM|LINK

  i have a sql table like

  name      toffees

  rajeev     12

  raj           14

  rajeev     16

  now  the following code i have in aspx.cs

  sqlcommad cmd=n ew sqlcommad("select sum(toffee) from table where name='ravi'");

  sqldatareader dr=cmd.executereader();

  if(dr.read)

  {

  label.text=dr.getint(0);

  }

  else

  {

  label.text="0"

  }
  

  problem cms here even there is no name in table with ravi still dr reads when i debug my programm and show me null excepton as it returns null value form table.why it is not going in else part

   

  someone pls help me??????????

  With Regards
  Rajeev Kumar
  
  Mark As Answer If It Helps You
  
  • Moved by XIII on Sep 19, 2010 07:03 AM
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  reza141414

  Participant

  1571 Points

  497 Posts

  Re: data reader problem

  Sep 19, 2010 07:49 AM|LINK

  hi...

  use: dr.HasRow to find out whether u have any row or not....

  ............................

  
  

  www.hotelsystem.ir
  dont forget to mark as answerd...
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  ketan_al

  Contributor

  6850 Points

  1143 Posts

  Re: data reader problem

  Sep 19, 2010 08:10 AM|LINK

  Hi,

  You can use SqlDataReader.IsDBNull, please refer following

  http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqldatareader.isdbnull%28v=VS.90%29.aspx

  hope this helps
  

  Ketan A. Lohar
  MCP, MCTS ( ASP.NET 3.5 )
  
  Please mark as answer if it helps :)
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  reza141414

  Participant

  1571 Points

  497 Posts

  Re: data reader problem

  Sep 19, 2010 08:11 AM|LINK

  hi...

  also i suggest u  to use LIKE sql statment  for comparing strings...
  

  go here to learn more:

  http://www.w3schools.com/SQL/sql_like.asp
  

  .......................................

  dont forget to mark as answerd...
  

  www.hotelsystem.ir
  dont forget to mark as answerd...
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  sansan

  All-Star

  53942 Points

  8147 Posts

  Re: data reader problem

  Sep 19, 2010 09:26 AM|LINK

  Firstly, you do not need to use a datareader when you are retrieving just one value. Use ExecuteScalar instead

  SqlConnection con = new SqlConnection("your connection string");
  try
  {
      Label Label1 = new Label();
      SqlCommand cmd = new SqlCommand("select ISNULL(sum(toffee),0) toffee from table where name='ravi'", con);
      con.Open();
      Label1.Text = cmd.ExecuteScalar().ToString();
      con.Close();
  }
  catch (Exception ex)
  {
  }
  finally
  {
      if (con.State == System.Data.ConnectionState.Open)
          con.Close();
      con.Dispose();
  }

  And you can use  ISNULL function to get 0 if no records are found.

  Santhosh
  • Marked as answer by Wencui Qian - MSFT on Sep 24, 2010 07:22 AM
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  DeerBear

  Member

  47 Points

  25 Posts

  Re: data reader problem

  Sep 19, 2010 09:58 AM|LINK

  rajeevinime

  i have a sql table like

  name      toffees

  rajeev     12

  raj           14

  rajeev     16

  now  the following code i have in aspx.cs

  sqlcommad cmd=n ew sqlcommad("select sum(toffee) from table where name='ravi'");

  [snip]
  

  problem cms here even there is no name in table with ravi still dr reads when i debug my programm and show me null excepton as it returns null value form table.why it is not going in else part

  someone pls help me??????????

  
  

  Simply, because there's no "ravi" record - at least among the shown ones :-) and you might not have it at all in your table :-)

  One advice, it works for me and it may work for you as well :-)

  When I am doing SQL statements, no matter the technology of destination, I always try them in the default query environment first, be it SQLServer Management Studio or something else. When I'm sure it works, I move it in code.

  Cheers,

  Andrew
  

  Mr. Andrea Raimondi
  Senior Software Analyst/Developer