Clear value of numericUpDown

domainUpDown1.ResetText();

this is used to reset the domain up down

You are wasting your time trying to do this.

You can clear the 'Text property by setting it to the empty string, but the Value remains unchanged.

You could call the 'DownButton or 'UpButton methods of the NumericUpDown, and that would decrement, or increment, the Value by the 'Increment Property Value, but under-the-hood that's still setting the 'Value property.

If you are trying to simulate a user manipulating the Control for software testing, then this CodeProject article may be useful: [^]. This CodeProject article is an overview of the open-source testing automation tool 'White: [^].

This open-source tool for .NET simulation of mouse and keyboard activity was just mentioned in CP QA yesterday: [^]:

"The Windows Input Simulator provides a simple .NET (C#) interface to simulate Keyboard or Mouse input using the Win32 SendInput method. All of the Interop is done for you and there's a simple programming model for sending multiple keystrokes."

There are a number of 3rd. party tools, open-source, and commercial for automation for .NET software testing, discussed here: [^].