Nested For....Loop!! HELP

[martin_d_bell]

Hi All,

 

I am quite new to programming and have grasped most things except for Nested For Loops which just will not click!!

 

I am trying to write a small application which loops through two datasets and compares values in dataset1 to the values in dataset2. So far my code looks like this

 

lblCheckDone.Visible = False
       lvbPartCodes.Items.Clear()

       If IsDBNull(DsPOPPartCodes1.POP_Parts_Costs) = False Then DsPOPPartCodes1.POP_Parts_Costs.Clear()
       SqlDAPOPPartCodes.Fill(DsPOPPartCodes1.POP_Parts_Costs)

       If IsDBNull(DsWDPartCodes1.POP_WDPcodes) = False Then DsWDPartCodes1.POP_WDPcodes.Clear()
       SqlDAWDPartCodes.Fill(DsWDPartCodes1.POP_WDPcodes)

       Dim x As Int16
       Dim y As Int16
       Dim PCode As String
       Dim PCodeDesc As String
       Dim Counter As String

       x = 0
       y = 0
       Counter = 0

       For y = 0 To DsWDPartCodes1.POP_WDPcodes.Rows.Count - 1

           PCode = DsWDPartCodes1.POP_WDPcodes.Rows(y).Item(1)
           PCodeDesc = DsWDPartCodes1.POP_WDPcodes.Rows(y).Item(2).ToString

           For x = 0 To DsPOPPartCodes1.POP_Parts_Costs.Rows.Count - 1

               If " " + Replace(PCodeDesc, ",", "") <> DsPOPPartCodes1.POP_Parts_Costs.Rows(x).Item(2).ToString Then

                   Dim lvbPartRow As New ListViewItem(PCode)
                   lvbPartRow.SubItems.Add(PCodeDesc)
                   lvbPartCodes.Items.Add(lvbPartRow)

                   Counter = Counter + 1
                   lblCheckDone.Text = Counter
                   Exit For
               End If
           Next
       Next
       SqlDAWDPartCodes.Update(DsWDPartCodes1.POP_WDPcodes)
       lblCheckDone.Visible = True

 

I have a listview and a button on my form, when the user clicks the button the values which do not match need to be displayed in the listview.

 

I just need help with the Nested For Loop as at the minute it lists all of the values in the ListView whether they match up or not.

 

Thanks

Martin

[Afraits]

Your problem is that the condition on the if statement is '<>', that means if any row in the second dataset differs from the one in the first being checked you will add to the list box.

 

matched=false
For x = 0 To DsPOPPartCodes1.POP_Parts_Costs.Rows.Count - 1

               If " " + Replace(PCodeDesc, ",", "") = DsPOPPartCodes1.POP_Parts_Costs.Rows(x).Item(2).ToString Then
                  matched=true
                  Exit For
               End If
Next
if matched=false then
Dim lvbPartRow As New ListViewItem(PCode)
 lvbPartRow.SubItems.Add(PCodeDesc)
 lvbPartCodes.Items.Add(lvbPartRow)

 Counter = Counter + 1
 lblCheckDone.Text = Counter
endif

 

This logic will fix the problem.

 

One other point - if the data is in datasets - why not have the data loaded into 2 tables in the same dataset then running an outer join SQL query between the tables to select ones that don't match?

[martin_d_bell]

Query

 

Thanks for the advice on using a query with an outer join. That works perfect and saves me having to program anything! Sometimes you can overcomplicate things and forget somebody else has programmed the tools to do the job.

 

Thanks again