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ado.net question to find specific row

Posted on 2008-10-09
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Last Modified: 2012-05-05
I have this datareader connection below.  How can I get first row or second or third?

     Try
Dim conn As New Data.SqlClient.SqlConnection(ConfigurationSettings.AppSettings("connectionUSSL"))
           
       conn.Open()
        Dim cmd As New Data.SqlClient.SqlCommand("dbo.wmItemOptionGroupsbyLevelSp", conn)
        cmd.CommandType = CommandType.StoredProcedure

        'cmd.Parameters.Add("@ID", SqlDbType.Int).Value = Request.QueryString("id").ToString()
        Dim dr As Data.SqlClient.SqlDataReader = Nothing
 
        dr = cmd.ExecuteReader()
 
       While dr.Read()
 
           Session("description") = dr("description").ToString()
         
           
       End While
 
        conn.Close()
        conn.Dispose()
Catch
End Try
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Question by:gianitoo
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13 Comments
 
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Expert Comment

by:Kevin Cross
ID: 22679565
One method is to put your results into a DataSet/DataTable: http://msdn.microsoft.com/en-us/library/system.data.datatable.aspx

If you define what the primary key column(s) on DataTable you can use its functionality to find specific row based on id value.
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Expert Comment

by:Kevin Cross
ID: 22679616
Here is an example from one of my programs to help with concept:
Dim columns(2) As DataColumn, dtKeys(1) As DataColumn
Dim dt As New DataTable()
Dim dr As DataRow
 
columns(0) = New DataColumn("ID", Type.GetType("System.String"))
columns(1) = New DataColumn("Value", Type.GetType("System.Double"))
dtKeys(0) = columns(0)
 
dt.Columns.AddRange(columns)
dt.PrimaryKey = dtKeys
 
dr = dt.Rows.Find("MyID")

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Expert Comment

by:prairiedog
ID: 22679801
While dr.Read() is a loop, if you still want to keep SqlDataReader, then you can do something like this:

Dim i As Integer
If (dr.HasRows) Then 'Always to check before retrieving
  While dr.Read() 
   If (i = 1) Then ' i=1 for the second row, i=2 third row, etc
     Session("description") = dr("description").ToString()   
   End If
   i += 1       
  End While
End If

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Expert Comment

by:prairiedog
ID: 22679822
Sorry, forgot to assign value to "i"
Dim i As Integer = 0

Dim i As Integer = 0
If (dr.HasRows) Then 'Always to check before retrieving
  While dr.Read() 
   If (i = 1) Then ' i=1 for the second row, i=2 third row, etc
     Session("description") = dr("description").ToString()   
   End If
   i += 1       
  End While
End If

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Author Comment

by:gianitoo
ID: 22681946
when i use this
While dr.Read()
            Session("description") = dr("description").ToString()
       End While
I get a result
when i use that one below i get zero results ????

Dim i As Integer = 0
If (dr.HasRows) Then 'Always to check before retrieving
  While dr.Read()
   If (i = 1) Then ' i=1 for the second row, i=2 third row, etc
     Session("description") = dr("description").ToString()  
   End If
   i += 1      
  End While
End If
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Expert Comment

by:prairiedog
ID: 22681993
"if (i=1) Then" is looking for the second record in dr, but if you have only one record, then you will get nothing.
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Author Comment

by:gianitoo
ID: 22682007
i have 4 records
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Accepted Solution

by:
prairiedog earned 500 total points
ID: 22682077
Set a break point on While dr.Read() to see how the code is executed.
Also add Exit While after Session so you don't have to loop through the whole set if you find the row.
The code works for me.

Dim i As Integer = 0
If (dr.HasRows) Then 'Always to check before retrieving
  While dr.Read() 
   If (i = 1) Then ' i=1 for the second row, i=2 third row, etc
     Session("description") = dr("description").ToString()  
     Exit While 
   End If
   i += 1       
  End While
End If

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Expert Comment

by:Kevin Cross
ID: 22682200
Debugging would be good as you have a TRY/CATCH in your code above, so if you are getting a SQL exception of other error you will not see it since CATCH block is empty.

Removing that or adding a trace write there will help troubleshoot as well.
0
 
LVL 1

Author Comment

by:gianitoo
ID: 22682243
This is my connection below.  ur code is not running and i can tell because i added else statement and still get no data ????

Dim conn As SqlConnection = ConfigurationManager.ConnectionStrings("test").ConnectionString
           
        conn.Open()
        Dim cmd As New Data.SqlClient.SqlCommand("wmItemOptionGroupsbyLevelSp", conn)
        cmd.CommandType = CommandType.StoredProcedure

        'cmd.Parameters.Add("@ID", SqlDbType.Int).Value = Request.QueryString("id").ToString()
        Dim dr As Data.SqlClient.SqlDataReader = Nothing
 
        dr = cmd.ExecuteReader()
 
        'While dr.Read()
 
        '    Label1.Text = dr("description").ToString()
         
           
        'End While
        Dim i As Integer = 0
        If (dr.HasRows) Then 'Always to check before retrieving
            While dr.Read()
                If (i = 4) Then ' i=1 for the second row, i=2 third row, etc
                    Session("description") = dr("description").ToString()
                    Exit While
                End If
                i += 1
            End While
        Else
            Label1.Text = "no data"
        End If

 
        conn.Close()
        conn.Dispose()
0
 
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Expert Comment

by:prairiedog
ID: 22682320
You only have 4 records, but i=4 is looking for the fifth record, that it why.
Option 1: Change i=4 to i=3
Option 2: Dim i As Integer = 1
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Author Comment

by:gianitoo
ID: 22682362
this is what i have and nothing yet
  Dim i As Integer = 1
        If (dr.HasRows) Then 'Always to check before retrieving
            While dr.Read()
                If (i = 3) Then ' i=1 for the second row, i=2 third row, etc
                    Session("description") = dr("description").ToString()
                    Exit While
                End If
                i += 1
            End While
        Else
            Label1.Text = "no data"
        End If
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LVL 22

Expert Comment

by:prairiedog
ID: 22682414
Did you use the break point as I mentioned before to step into your code?
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