C# Find top 3 in Collection list box

Question

Find Top 3 Button – which processes the data to find the 3 highest sales amounts and displays these sales persons names along with their place (1st, 2nd, 3rd), and sales amount.

I have two list boxes I just want to find the top 3 highest sales persons with their sales amount and show them as message box to the user in 3 separate lines

Picture of the application: http://s17.postimg.org/6dvo3a4qn/Untitled.jpg

Listboxes names: lstNames, lstTotalSales

My find top 3 button code is:

private void btnFindTop3_Click(object sender, EventArgs e)
{
    decimal dec1HighestAmount = 0;
    decimal dec2HighestAmount = 0;
    decimal dec3HighestAmount = 0;
    for (int Index = 0; Index < lstTotalSales.Items.Count; Index++)
    {
        if (Convert.ToDecimal(lstTotalSales.Items[Index]) > dec1HighestAmount)
        {
            dec1HighestAmount = Convert.ToDecimal(lstTotalSales.Items[Index]);
        }
        if (Convert.ToDecimal(lstTotalSales.Items[Index]) < dec1HighestAmount)
        {
            dec2HighestAmount = Convert.ToDecimal(lstTotalSales.Items[Index]);
        }
        if (Convert.ToDecimal(lstTotalSales.Items[Index]) < dec2HighestAmount)
        {
            dec2HighestAmount = Convert.ToDecimal(lstTotalSales.Items[Index]);
        }
    }
    MessageBox.Show("Highest Amount is " + dec1HighestAmount + " and " + dec2HighestAmount + " and " + dec3HighestAmount);
}

This is the code that I used to fill the listboxes:

public partial class Form1 : Form
{
    List<decimal> lstTotal = new List<decimal>();
    public Form1()
    {
        InitializeComponent();
    }

    private void btnReadInSalesData_Click(object sender, EventArgs e)
    {
        openFileDialog1.FileName = "SalesNumbers.txt";
        if (openFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK) //If and Open Dialog OK
        {
            StreamReader srFile = File.OpenText(openFileDialog1.FileName);

            decimal decTotal = 0;

            while (!srFile.EndOfStream)
            {
                string strline = srFile.ReadLine();
                string[] strSplit = strline.Split('$');

                foreach (string strSplittedOutput in strSplit)
                {

                    if (decimal.TryParse(strSplittedOutput, out decTotal))
                    {
                        lstTotal.Add(decTotal);
                        lstTotalSales.Items.Add(strSplittedOutput);
                    }
                    else //else than decimals add strings
                    {
                        lstNames.Items.Add(strSplittedOutput); //add the Sales men names to lstNames listbox
                    }
                }
            } //End of while

            srFile.Close(); //Close StreamReader
        }
        else
            MessageBox.Show("User Cancel Read File Operation."); // if the user cancel the read file operation show this messagebox

        // ... ??
    }

    // ...
}

Thank you

Answer 1

something like

var top_three = (from sales in lstTotalSales.Items
                 orderby sales descending
                 select sales).Take(3);

will hold your top 3 using linq...

---

Argh ... ok ... the bad news ... you have lots of work ahead of you ... the good news, this will set you on the right way:

public partial class Form1 : Form
{
    List<decimal> lstTotal = new List<decimal>();
    List<SalesPerson> lstSalesPerson = new List<SalesPerson>;

    public Form1()
    {
        InitializeComponent();
    }

    private void btnReadInSalesData_Click(object sender, EventArgs e)
    {
        openFileDialog1.FileName = "SalesNumbers.txt";
        if (openFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK) //If and Open Dialog OK
        {
            StreamReader srFile = File.OpenText(openFileDialog1.FileName);

            decimal decTotal = 0;
            decimal tempSales =0;
            string tempName = "";

            while (!srFile.EndOfStream)
            {
                string strline = srFile.ReadLine();
                string[] strSplit = strline.Split('$');

                // I'll seriously assume this happens only twice ...
                foreach (string strSplittedOutput in strSplit)
                {

                    if (decimal.TryParse(strSplittedOutput, out decTotal))
                    {
                        lstTotal.Add(decTotal);
                        lstTotalSales.Items.Add(strSplittedOutput);
                        tempSales = strSplittedOutput;
                    }
                    else //else than decimals add strings
                    {
                        lstNames.Items.Add(strSplittedOutput); //add the Sales men names to lstNames listbox
                        tempName = strSplittedOutput;
                    }
                }

                    // Adding this to our people list ...
                    lstSalesPerson.Add(new SalesPerson {Name=tempName,TotalSales=tempSales});

            } //End of while

            srFile.Close(); //Close StreamReader
        }
        else
            MessageBox.Show("User Cancel Read File Operation."); // if the user cancel the read file operation show this messagebox

        // ... ??
    }

    // ...
}


public class SalesPerson {
    public string Name {get; set;}
    public decimal TotalSales {get; set;}
}

I've added a class called SalesPerson ... this objects has a Name and a TotalSales ... doooohhh ... In your loop, I'm assuming you a have a text file with lines and in each one name and sales value ... I've added at the end the creation of a SalesPerson that goes into your lstSalesPerson (added at the top).

Now we're almost there ... Please go read and understand this article: http://www.codeproject.com/Articles/671544/Understanding-SelectedValue-SelectedValuePath-Sele .

Once you do, you'll realize you don't need to have the lstTotalSales and the lstNames , because you can just link those listboxes to the DisplayMemberPath of your lstSalesPerson .

Now, when you select your top 3 using the linq above, you have 3 objects. For each object you can use the values Name and TotalSales since they are just properties on that object.

var top_three = (from person in lstSalesPerson
             orderby person.TotalSales descending
             select person).Take(3);

foreach (var person in top_three) {
     // do something with person.Name
     // do something with person.TotalSales
}