Message =輸入字符串的格式不正確。 在C＃中

Question

我轉換為double的第一個while循環中引發以下異常：

System.FormatException
  HResult=0x80131537
  Message=Input string was not in a correct format.
  Source=mscorlib
  StackTrace:
   at System.Number.ParseDouble(String value, NumberStyles options, NumberFormatInfo numfmt)
   at System.Convert.ToDouble(String value)
   at WindowsFormsApp6.Form1.button1_Click(Object sender, EventArgs e) in C:\Users\King\source\repos\WindowsFormsApp6\WindowsFormsApp6\Form1.cs:line 52
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at WindowsFormsApp6.Program.Main() in C:\Users\King\source\repos\WindowsFormsApp6\WindowsFormsApp6\Program.cs:line 19

我不確定自己寫錯了什么或如何解決此問題。 我正在讀取一個csv文件。 我已經進行測試，以確保數據從一個變量傳遞到另一個變量。 數據被流讀取器讀取，並存儲在一維數組中，這些數組被保存到一個變量中，用於比較數據點以確定數據集中的所有峰和谷

這是我的程序：

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;
using System.IO;

namespace WindowsFormsApp6
{
    public partial class Form1 : Form
    {
        double firstY = 0.0;

        string testX;
        string testY;

        string[] xpoint = new string[5000];
        string[] ypoint = new string[5000];

        private void button2_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            using (var reader = new StreamReader(@"D:\data.csv"))
            {
                while (!reader.EndOfStream)
                {
                    string line = reader.ReadLine();
                    var values = line.Split(',');

                    testX = values[0];
                    testY = values[1];

                    if (firstY == 0.0)
                    {
                        firstY = Convert.ToDouble(testY);
                        Convert.ToString(testY);
                    }

                    while (Convert.ToDouble(testY) >= firstY)//where error is
                    {
                        firstY = Convert.ToDouble(testY);

                        if (firstY == Convert.ToDouble(testY))
                        {
                            break;
                        }

                        if (Convert.ToDouble(testY) < firstY)
                        {
                            listBox1.Items.Add(Convert.ToDouble(testX) + "," + firstY);

                            break;
                        }

                        break;
                    }

                    while (Convert.ToDouble(testY) < firstY)
                    {
                        firstY = Convert.ToDouble(testY);

                        if(firstY == Convert.ToDouble(testY))
                        {
                            break;
                        }

                        if (Convert.ToDouble(testY) > firstY)
                        {

                            listBox2.Items.Add(Convert.ToDouble(testX) + "," + firstY);

                            break;
                        }

                        break;
                    }

                    Convert.ToString(testX);
                    Convert.ToString(testY);
                }
            }
        }
    }
}

Answer 1

csv文件中的某個地方存在一個無法轉換為雙精度值的值。
為避免此異常，請用Double.TryParse替換所有的Convert.ToDouble 。 如果該值可以解析為double則返回true否則，則返回false 。

話雖如此，其余的代碼沒有任何意義。 如果您看這部分，例如：

                while (Convert.ToDouble(testY) >= firstY)//where error is
                {
                    firstY = Convert.ToDouble(testY);

                    if (firstY == Convert.ToDouble(testY))
                    {
                        break;
                    }

假設轉換為double可以，那么您的代碼將檢查firstY == Convert.ToDouble(testY) ，由於firstY是Convert.ToDouble(testY)的結果，因此它將始終返回true ，因此您會跳出循環，從不進入第二個循環，因為它的條件是while (Convert.ToDouble(testY) < firstY) -您現在應該知道它們是相同的值...

我猜您在代碼中混用了testY和testX 。

Answer 2

這是我需要防止拋出異常的代碼（對於可能接收相同異常並且不確定原因的任何人），您需要將兩個變量的轉換放在“ try / catch”中。 像這樣：

try
{
    testX = Convert.ToDouble(values[0]);
    testX = Convert.ToDouble(values[1]);
}
catch
{
}