removing duplicates

havey · February 25th, 2008, 07:18 PM

Hi in my example i hope i'm not being overly complicated for the simple task at hand. I'm calling much data from a table and there are multiple duplicate label names. I need every record being pulled, but in this case i'm hoping to display only the unique names from the data. So imagine a thousand records with label being from 1 to 10, there are many duplicate label names. This is what i've tried to do to get only the unique in a DataList to display them in the aspx page (am i being overly complicated..?) I'm having issues getting it working, any thoughts?

Code:

        static List<string> removeDuplicates(List<string> inputList)
        {
            List<string> finalList = new List<string>();
            foreach (string currValue in inputList)
            {
                if (!Contains(finalList, currValue))
                {
                    finalList.Add(currValue);
                }
            }
            return finalList;
        }

        static bool Contains(List<string> list, string comparedValue)
        {
            foreach (string listValue in list)
            {
                if (listValue == comparedValue)
                {
                    return true;
                }
            }
            return false;
        }

        protected void dlGoalsDataBound(object sender, DataListItemEventArgs e)
        {
            ArrayList Goals = new ArrayList();
            Goals.Add(e);

            List<string> result = removeDuplicates(Goals[0]);

            result.ForEach(
                delegate(string s)
                {
                HyperLink tmpLnk = (HyperLink)e.Item.FindControl("HyperLink1");
                Label tmpLbl = (Label)e.Item.FindControl("Label1");
                Session["GoalTypeID"] = tmpLbl.Text;
                tmpLnk.NavigateUrl = "~/area/default.aspx?nav=g&id=" + tmpLbl.Text + "";
                }
                ); 

        }

dparsons · February 25th, 2008, 08:09 PM

Why aren't you just doing a SELECT DISTINCT from your database?

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havey · February 25th, 2008, 08:19 PM

cause i'm not using the db query exclusive for this, thanks

samjudson · February 26th, 2008, 06:10 AM

Code:

ArrayList Goals = new ArrayList();
Goals.Add(e);

List<string> result = removeDuplicates(Goals[0]);

The above section of code is nonsense. You create an array, add 'e' to it and then pass the first element of the array (which will be 'e') to the function. This is therefore equivalent to the following:

Code:

List<string> result = removeDuplicates(e);

However - I suspect that 'e' is not List<string> so I am suprised this code even compiles, let alone runs.

Also, List<string> already contains a Contains method.

Code:

static List<string> removeDuplicates(List<string> inputList)
{
  List<string> finalList = new List<string>();

  foreach(string s in inputList)
  {
    if( !finalList.Contains(s) ) finalList.Add(s);
  }
  return finalList;
}

However, this does not get around the issue of where you get the first list from.

/- Sam Judson : Wrox Technical Editor -/

havey · February 26th, 2008, 09:22 AM

samjudson

[2]the added contain actually speeds up the processing.

[1]Thanks for the first part, your correct

samjudson · February 26th, 2008, 09:44 AM

Another alternative which should definitely be quicker would be to Sort the list and then use the RemoveAll with a predicate to remove the duplicates:

Code:

result.Sort();
result.RemoveAll(RemoveDuplicates);

private static string lastString = String.Empty;

private static bool RemoveDuplicates(string a)
{
  if( a == lastString )
  {
    return true;
  }
  lastString = a;
  return false;
}

/- Sam Judson : Wrox Technical Editor -/

David_0223 · February 26th, 2008, 11:01 AM

Havey,

Why don't you use a SortedDictionary with a try block around the Add to catch duplicates. In the example I am assuming that DataListItemEventArgs is an array of DataListItemEventArg and that DataListItemEventArg is an object with a property named "Goal". Of course, only you know what DataListItemEventArgs is so you may have to adapt the example accordingly.

I.E.:

Code:

protected void dlGoalsDataBound(object sender, DataListItemEventArgs e)
{

  // Create a new sorted dictionary of DataListItemEventArg, with string
  // keys.
  SortedDictionary<string, DataListItemEventArg> Goals = 
    new SortedDictionary<string, DataListItemEventArg>();

  for(int i=0;i<e.Length;i++) 
  {
    // The Add method throws an exception if the new key is 
    // already in the dictionary.
    try
    {
      Goals.Add((DataListItemEventArg)e[i].Goal, e[i]);
    }
    catch (ArgumentException)
    {
      Console.WriteLine("The Goal {0} has already been added.", e[i].Goal);
    }
  }

  ... more code here ...
}

This would combine sorting the data as you input it and eliminating duplcates.

What you don't know can hurt you!

havey · February 26th, 2008, 01:04 PM

thanks David, i tried that kinda method and had issues converting generic list to collection array.

Maybe i need to explain my self better...sry,
there is default.aspx page that uses a masterPage. In the default.aspx.cs there is:

Code:

List<HealthGoal> goals = null;

goals = SiteProvider.Member.GetGoalsForMember(Convert.ToInt32(Session["PersonID"]));

..... create an xml string of the values to pass to the default.aspx via Page.ClientScript...blah blah
.....

now the goals[i].GoalTypeID (numeric) is what i want the unique list of.

In the master page.aspx i have:

Code:

<asp:DataList ID="dlResults" runat="server" OnItemDataBound="dlResultsDataBound" Width="150">
                                                    <ItemTemplate>
                                                        <table width="100%" border="0" cellspacing="0" cellpadding="0">
                                                            <tr>
                                                                <td width="1%" valign="top"><img alt="" src="/images/members-area/subnav-bullets/green.gif" width="28" height="20"></td>
                                                                <td valign="top">
                                                                    <asp:HyperLink CssClass="subnav" ID="HyperLink1" runat="server"><%# Container.DataItem %></asp:HyperLink>
                                                                    <asp:Label ID="Label1" runat="server" Text='<%# Container.DataItem %>' Visible="false"></asp:Label>
                                                                </td>
                                                            </tr>
                                                        </table>
                                                    </ItemTemplate>
                                                </asp:DataList>

and the behind code is the where the code were are talking about should go. So now that you have the whole picture, any ideas how to DataBind the unique list of goals[i].GoalTypeID

I'm trying to incorporate your diction idea, as i think your thought has much validity, this is what i'm starting with:

Code:

protected void dlGoalsDataBound(object sender, DataListItemEventArgs e)
        {

            ArrayList DataListItemEventArg = new ArrayList();

            DataListItemEventArg = SiteProvider.Member.GetGoalsForMember(Convert.ToInt32(Session["PersonID"]));

            SortedDictionary<string, DataListItemEventArg> Goals = new SortedDictionary<string, DataListItemEventArg>();

            for (int i = 0; i < e.Length; i++)
            {
                try
                {
                    Goals.Add((DataListItemEventArg)e[i].Goal, e[i]);
                }
                catch
                {
                   //
                }
            }

            dlGoals.DataSource = Goals;
            dlGoals.DataBind();
        }

samjudson · February 26th, 2008, 01:14 PM

DataListItemEventArgs is just a wrapper for the event arguments fired by the data grid, I think you're getting it confused with something.

http://msdn2.microsoft.com/en-us/lib...eventargs.aspx

This should work:

Code:

List<HealthGoal> goals = SiteProvider.Member.GetGoalsForMember(Convert.ToInt32(Session["PersonID"]));

List<int> finalGoals = new List<int>();

foreach(HealthGoal g in goals)
{
  if( !finalGoals.Contains(g.GoalTypeId) )
  {
    finalGoals.Add(g.GoalTypeId);
  }
}

dlGoals.DataSource = finalGoals;
dlGoals.DataBind();

/- Sam Judson : Wrox Technical Editor -/

havey · February 26th, 2008, 02:05 PM

Thanks, thank you very much