Why am I getting an exception InvalidOperationException?
Solution 1
You are removing items from LocalyKeyWords
while in the midst of iterating over it; that is not allowed, as the exception message says.
I 'm not sure what the big picture is here, but a localized solution would be to make a temporary copy of LocalyKeyWords
and iterate over that. You can then modify the "source" collection without any trouble.
Example:
foreach (var kvp in LocalyKeyWords.ToList()) // .ToList() makes a temp copy
Solution 2
You can't modify the IEnumerable collection inside of foreach
.
You can create a copy of the dictionary and loop through it modifing the original one.
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user2065612
Updated on September 15, 2022Comments
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user2065612 over 1 year
I have written the following code which removes the selected value from the listBox. I also want to remove it from the Dictionary List and then update/write it to the text file so when I run the program again and load the text file it will be updated if not it will keep showing the removed item each time I run my application again.
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 is a Dictionary>
In this case it contain two items/keys I remove one and I see with a breakpoint that this one have been removed.
The question is if I need to remove the kvp.Key or to remove somehow the item I removed from the listBox wich is the one I want to remove from the LocalyKeywords and it's the obj variable since im doing:
data.Remove(obj);
So maybe I need to remove obj also from the localyKeyWords ?
The excpetion the error im getting is after it's removing the item from the LocalyKeyWords an click continue on this line:
foreach (KeyValuePair<string, List<string>> kvp in LocalyKeyWords)
Im getting the error:
Collection was modified; enumeration operation may not execute
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: