C#

class IPCMsgHandler
{
	private Thread listenThread = new Thread(ListeningThreadFunc);

...

	public void Start()
	{
		listenThread.Start(this);
	}

	private static void ListeningThreadFunc(object data)
	{
		IPCMsgHandler helper = data as IPCMsgHandler;

		...

		//helper.OnMessage(); doesn't work...staying in current thread context

		MethodInvoker mi = new MethodInvoker(helper.OnMessage);
		mi.Invoke();

		...
	}
}

public class AutoCADApplication : IExtensionApplication
{
	IPCMsgHandler helper = null;

	public void Initialize()
	{
		// I have the right execution-context here
		this.helper = new IPCMsgHandler("AutoCAD-IPCServer", new IPCMsgHandler.MessageHandler(this.OnIPCMessage));
		this.helper.Start();
	}
	private void OnIPCMessage()
	{
		// I have the WRONG execution-context here
		return;
	}

sw1.Start(); 
for (int k = 0; k < 500; k++) 
{
  longWord.Remove(longWord.Length - 10, 10);
}
sw1.Stop(); 

buchstaben wrote:

another point is, that a test 3 (removing backwards) will run in 0ms (?!):

static class ExtMethod
    {
        public static StringBuilder SubString(this StringBuilder sr1, int startPos, int length)
        {
            StringBuilder randomString = new StringBuilder();
            char[] charArray = new char[length];
            sr1.CopyTo(startPos, charArray, 0, length);
            randomString.Append(charArray);
            return randomString;
        }
    }

// We know how long the output needs to be, so preallocate capacity
StringBuilder output = new StringBuilder(length);
 
for ( int i = 0; i < length; ++i )
{
   output.Append( sr1.Chars[i] );
}
 
return output;