C# 我不确定你的具体问题是什么。关于写一个能吸引最多答案的问题的技巧，请看。我想这不是家庭作业网站！！家庭作业问题很好，我鼓励学习者提问，我认为这个问题需要一点拼写检查，因为我想帮助他们，但不知道他们需要什么。我更新了我的帖子，抱歉，如果我不清楚。哇，非常感谢

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我不确定你的具体问题是什么。关于写一个能吸引最多答案的问题的技巧，请看。我想这不是家庭作业网站！！家庭作业问题很好，我鼓励学习者提问，我认为这个问题需要一点拼写检查，因为我想帮助他们，但不知道他们需要什么。我更新了我的帖子，抱歉，如果我不清楚。哇，非常感谢！这正是我需要的。现在我知道了，以备将来参考。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace BsweeneyCsharp3_1_
{
    public partial class Form1 : Form
    {
        List<double> values;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            values = new List<double>();
        }

        void ShowValues()
        {
            listBox1.Items.Clear();

            for (int i = 0; i < values.Count; i++)
                listBox1.Items.Add(values[i]);
        }

        private void button1_Click(object sender, EventArgs e)
        {

            double value = 0.00;
            double sum = 0.00, sumSquares = 0.00, squareSums;
            double stdDev = 0.00, mean = 0.00;

            if (textBox1.Text.Length == 0)
            {
                MessageBox.Show("You must enter a value.", "Standard Deviation");
                return;
            }

            try
            {               
                value = double.Parse(textBox1.Text);              
                values.Add(value);
                ShowValues();
                textBox1.Text = "";
                textBox1.Focus();
            }
            catch (FormatException)
            {
                MessageBox.Show("The value you entered is invalid.",
                                "");
            }

            for (int i = 0; i < values.Count; i++)
            {
                sum += values[i];
            }
            mean = sum / values.Count;
            squareSums = sum * sum;

            for (int i = 0; i < values.Count; i++)
                sumSquares += (values[i] * values[i]);

            double numerator = values.Count * sumSquares - squareSums;
            double denominator = values.Count * (values.Count - 1);
            stdDev = Math.Sqrt(numerator / denominator);

            textBox2.Text = mean.ToString();

            textBox3.Text = stdDev.ToString("F");

        }

        private void button2_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.Filter = "TXT|*.txt";
            double mean = 0.00, stdDev = 0.00, sum = 0.00;
            double sumSquares = 0.00, squareSums = 0.00;
            int counter = 0;

            if (ofd.ShowDialog() == DialogResult.OK)
            {
                textBox4.Text = ofd.FileName;
            }

            string line;
            System.IO.StreamReader file = new System.IO.StreamReader(textBox4.Text);
            List<string> list = new List<string>();           

            while ((line = file.ReadLine()) != null)
            {                
                listBox2.Items.Add(line);
                var dbl = Convert.ToDouble(line);

                sum += dbl;                
                counter++;
            }
            if (counter > 0)
            {
                mean = sum / counter;
                squareSums += sum * sum;
            }
            if(counter > 0)
            {

                sumSquares += Math.Pow((sum - mean), 2);

                double numerator = counter * sumSquares - squareSums;
                double denominator = counter * (counter - 1);
                stdDev = Math.Sqrt(numerator / denominator);

                textBox2.Text = mean.ToString();

                textBox3.Text = numerator.ToString();
            }
        }
    }

}

    if (counter > 0)//you don't need the same check 2x
    {
        mean = sum / counter;
        for (int i = 0; i < listBox2.Items.Count; i++)
            sumSquares += (Convert.ToDouble(listBox2.Items[i]) * Convert.ToDouble(listBox2.Items[i]));
        squareSums += sum * sum;

        //sumSquares += Math.Pow((sum - mean), 2);//You changed the formula again here

        double numerator = counter * sumSquares - squareSums;
        double denominator = counter * (counter - 1);
        stdDev = Math.Sqrt(numerator / denominator);

        textBox2.Text = mean.ToString();

        //textBox3.Text = numerator.ToString();//You changed how you did things again
        textBox3.Text = stdDev.ToString("F");
    }