https://learn.microsoft.com/de-de/dotnet/api/system.windows.forms.control.checkforillegalcrossthreadcalls?view=netframework-4.8.1&redirectedfrom=MSDN
Control.CheckForIllegalCrossThreadCalls Property (System.Windows.Forms) | Microsoft Learn
Gets or sets a value indicating whether to catch calls on the wrong thread that access a control's Handle property when an application is being debugged.
property systemwindows formscontrolmicrosoftlearn