为什么我会得到一个异常InvalidOperationException

本文关键字：一个 异常 InvalidOperationException 为什么 | 更新日期: 2023-09-27 18:01:08

我已经编写了以下代码，它从listBox中删除了选定的值。我还想将它从字典列表中删除，然后更新/写入文本文件，这样当我再次运行程序并加载文本文件时，它会被更新，如果没有，每次我再次运行应用程序时，它都会继续显示删除的项目。

private void listBox1_KeyDown(object sender, KeyEventArgs e)
        {
            string sb;
            if (e.KeyCode == Keys.Delete)
            {
                if (this.listBox1.SelectedIndex >= 0)
                {
                    string obj = this.listBox1.SelectedValue.ToString();
                    data.Remove(obj);
                    listBox1.DataSource = null;
                    listBox1.DataSource = data;
                    foreach (KeyValuePair<string, List<string>> kvp in LocalyKeyWords)
                    {
                        for (int i = 0; i < kvp.Value.Count(); i++)
                        {
                            sb = "Url: " + kvp.Key + " --- " + "Local KeyWord: " + kvp.Value[i] + Environment.NewLine;
                            LocalyKeyWords.Remove(kvp.Key);
                        }
                    }
                }
            }
        }

LocalyKeyWords是一个字典>

在这种情况下，它包含两个项/键，我删除了其中一个，并通过断点看到这一个已被删除。

问题是我是否需要删除kvp。键或以某种方式删除我从列表框中删除的项目，它是我想从LocalyKeywords中删除的，它是obj变量，因为我正在做：

data.Remove(obj);

所以也许我也需要从localyKeyWords中删除obj？

我得到的错误解释是，在它从LocalyKeyWords中删除项目后，点击继续这一行：

foreach (KeyValuePair<string, List<string>> kvp in LocalyKeyWords)

我收到错误：

集合已修改；枚举操作可能无法执行

System.InvalidOperationException was unhandled
  HResult=-2146233079
  Message=Collection was modified; enumeration operation may not execute.
  Source=mscorlib
  StackTrace:
       at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
       at System.Collections.Generic.Dictionary`2.Enumerator.MoveNext()
       at GatherLinks.Form1.listBox1_KeyDown(Object sender, KeyEventArgs e) in d:'C-Sharp'GatherLinks'GatherLinks'GatherLinks'Form1.cs:line 959
       at System.Windows.Forms.Control.OnKeyDown(KeyEventArgs e)
       at System.Windows.Forms.Control.ProcessKeyEventArgs(Message& m)
       at System.Windows.Forms.Control.ProcessKeyMessage(Message& m)
       at System.Windows.Forms.Control.WmKeyChar(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)
       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 GatherLinks.Program.Main() in d:'C-Sharp'GatherLinks'GatherLinks'GatherLinks'Program.cs:line 18
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

为什么我会得到一个异常InvalidOperationException

您正在从LocalyKeyWords中删除项，同时正在对其进行迭代；正如异常消息所说，这是不允许的。

我不确定这里的大局是什么，但本地化的解决方案是制作LocalyKeyWords的临时副本并对其进行迭代。然后，您可以修改"源"集合，而不会出现任何问题。

示例：

foreach (var kvp in LocalyKeyWords.ToList())  // .ToList() makes a temp copy

您不能修改foreach内部的IEnumerable集合。

您可以创建字典的副本，并在其中循环修改原始字典。

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