c# - 为什么我收到异常错误 indexOutOfRangeException？

Question

在 Form1 构造函数中我有:

if (System.IO.File.Exists(keywords_path_file))
            {
                ListBoxLoadKeys(LocalyKeyWords, keywords_path_file);
            }
            else
            {
                fileExist = new StreamWriter(keywords_path_file);
                fileExist.Close();
                ListBoxLoadKeys(LocalyKeyWords, keywords_path_file);
            }

我使用断点并查看文件是否存在:

C:\Users\bout0_000\AppData\Local\GatherLinks\GatherLinks\Keywords\Keywords.txt

文件内容为:

http://www.walla.co.il,walla
http://www.cnet.com,cnet
http://rotter.net/forum/scoops1/29961.shtml,rotter
http://vanessawest.tripod.com/crimescenephotos.html,VanessaWest
http://rotter.net/forum/scoops1/45227.shtml,scoops
https://www.google.com/search?q=live+cameras,live camera
https://www.google.com/search?q=rape+images&oq=+images&aqs=chrome..69i57.1661j0&sourceid=chrome&ie=UTF-8,hi
https://www.google.com/search?q=+images&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=GqotUv2kA4OftAae94DoAg&biw=951&bih=457&sei=oaotUtDqM8WbtAag3IFg#hl=en&q=+and+&tbm=isch&um=1,chud
http://www.test.com,test

该文件包含 9 个键和关键字。键的左侧是关键字的右侧。

然后进入这个方法:

private void ListBoxLoadKeys(Dictionary<string, List<string>> dictionary, string FileName)
        {
            List<string> urls = new List<string>();
            using (StreamReader sr = new StreamReader(FileName))
            {
                while ((line = sr.ReadLine()) != null)
                {
                    int i = line.Count();
                    tokens = line.Split(',');
                    dictionary.Add(tokens[0], tokens.Skip(1).ToList());
                    data.Add("Url: " + tokens[0] + " --- " + "Localy KeyWord: " + tokens[1]);
                    urls.Add(tokens[0]);
                }
            }
            listBox1.DataSource = data;
            listBox1.Tag = urls;
        }

在下线的方法中:listBox1.DataSource = data;它跳跃并做这个事件:

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {

            if (listBox1.SelectedItem != null)
            {
                label4.Text = listBox1.SelectedItem.ToString();
                string startTag = "Url: ";
                string endTag = " ---";
                int startTagWidth = startTag.Length;
                int endTagWidth = endTag.Length;
                int index = 0;
                index = label4.Text.IndexOf(startTag, index);
                int start = index + startTagWidth;
                index = label4.Text.IndexOf(endTag, start + 1);
                string g = label4.Text.Substring(start, index - start);
                label4.Text = g;
                mainUrl = g;
            }
        }

最后我看到 data 和 listBox1.DataSource 都包含 9 个项目。

所有这一切之后，程序正在运行。我在 listBox 的右侧看到了键和关键字的项目。一旦我单击 listBox1 中的一个键，我就会在该行收到异常:

if (listBox1.SelectedItem != null)

在 listBox1_SelectedIndexChanged 事件中。

异常(exception)情况是:

索引超出了数组的范围

System.IndexOutOfRangeException was unhandled
  HResult=-2146233080
  Message=Index was outside the bounds of the array.
  Source=System.Windows.Forms
  StackTrace:
       at System.Windows.Forms.ListBox.ItemArray.GetItem(Int32 virtualIndex, Int32 stateMask)
       at System.Windows.Forms.ListBox.get_SelectedItem()
       at GatherLinks.Form1.listBox1_SelectedIndexChanged(Object sender, EventArgs e) in d:\C-Sharp\GatherLinks\GatherLinks-2\GatherLinks\GatherLinks\Form1.cs:line 543
       at System.Windows.Forms.ListBox.OnSelectedIndexChanged(EventArgs e)
       at System.Windows.Forms.ListBox.WmReflectCommand(Message& m)
       at System.Windows.Forms.ListBox.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.SendMessage(HandleRef hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
       at System.Windows.Forms.Control.SendMessage(Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.Control.ReflectMessageInternal(IntPtr hWnd, Message& m)
       at System.Windows.Forms.Control.WmCommand(Message& m)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
       at System.Windows.Forms.ContainerControl.WndProc(Message& m)
       at System.Windows.Forms.Form.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.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
       at System.Windows.Forms.NativeWindow.DefWndProc(Message& m)
       at System.Windows.Forms.Control.DefWndProc(Message& m)
       at System.Windows.Forms.Control.WmKillFocus(Message& m)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ListBox.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)
  InnerException: 

我知道异常是什么意思，但我得到了什么以及我该如何解决它？

例如，如果我在运行程序时先移动，并使用向上和向下键箭头在列表框中的键之间移动，然后我单击其中一个，我不会收到任何异常。当我运行程序并立即用鼠标单击列表框中的一个键时，会出现异常。

在它们之间移动然后单击其中一个是可以的，但首先单击其中一个会异常(exception)。

编辑**

我现在看到，在它转到 listBox1_SelectedIndexChanged 事件到此事件 istBox1 鼠标按下之前:

private void listBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (Control.ModifierKeys == Keys.Control || ( Control.ModifierKeys == Keys.Control || e.Button == MouseButtons.Left))
            {
                listBox1.SelectionMode = SelectionMode.MultiExtended;
            }
            else if (e.Button == MouseButtons.Left)
            {
                listBox1.SelectionMode = SelectionMode.One;
            }
        }

执行此行:

listBox1.SelectionMode = SelectionMode.MultiExtended;

然后回到selectedindexchanged事件，抛异常就行了:

if (listBox1.SelectedItem != null)

那也是行号:543

Answer 1

你不能这样做:

private void listBox1_MouseDown(object sender, MouseEventArgs e)
{
  if (Control.ModifierKeys == Keys.Control || ( Control.ModifierKeys == Keys.Control || e.Button == MouseButtons.Left))
  {
    listBox1.SelectionMode = SelectionMode.MultiExtended;
  }
  else if (e.Button == MouseButtons.Left)
  {
    listBox1.SelectionMode = SelectionMode.One;
  }
}

我认为，在 MouseDown 事件中更改该属性会破坏窗口并重新创建它，这会扰乱 SelectedIndexChanged 事件期间触发的内部信息。

只需注释掉该代码并在设计时决定 ListBox 控件应具有哪种 SelectionMode。

您还应该确保获得正确的索引值，例如:

index = label4.Text.IndexOf(endTag, start + 1);
if (index > -1) {
  string g = label4.Text.Substring(start, index - start);
  label4.Text = g;
}