C# 在集合列表框中查找前 3 名

Question

Find Top 3 Button – 处理数据以找到 3 个最高销售额 并显示这些销售人员的姓名以及他们的位置（1st、2nd、3rd）， 和销售额。

我有两个列表框，我只想找到销售额最高的前 3 名销售人员，并将他们作为消息框显示给用户，分 3 行显示

应用图片： http://s17.postimg.org/6dvo3a4qn/Untitled.jpg

列表框名称：lstNames、lstTotalSales

我找到前 3 个按钮的代码是：

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);
}

这是我用来填充列表框的代码：

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

        // ... ??
    }

    // ...
}

谢谢

Answer 1

类似

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

将使用 linq 保持前 3 名...

---

啊……好吧……坏消息……你还有很多工作要做……好消息，这会让你走上正确的道路：

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;}
}

我添加了一个名为 SalesPerson 的类 ...这个对象有一个 Name 和一个 TotalSales ...doooohhh ...在你的循环中，我假设你有一个带有线条的文本文件和在每个名称和销售价值中...我在最后添加了一个 SalesPerson 的创建，该 lstSalesPerson 进入您的 lstSalesPerson（添加在顶部）。

现在我们快到了……请阅读并理解这篇文章：http://www.codeproject.com/Articles/671544/Understanding-SelectedValue-SelectedValuePath-Sele。

一旦你这样做了，你就会意识到你不需要lstTotalSales和lstNames，因为你可以将这些列表框链接到你的lstSalesPerson的DisplayMemberPath。

现在，当您使用上面的 linq 选择前 3 个对象时，您有 3 个对象。对于每个对象，您可以使用值 Name 和 TotalSales，因为它们只是该对象的属性。

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
}