How to run my application when windows start up?

For that you need to create windows service.
Simple Windows Service Sample[^]

How to develop Windows Service in C#[^]

This line will add a registry entry for autostart:

Registry.CurrentUser.CreateSubKey(@"Software\Microsoft\Windows\CurrentVersion\Run").SetValue("keyNameForRegistry", "PATH_TO_EXECUTABLE");

And this line will remove the autostart:

Registry.CurrentUser.CreateSubKey(@"Software\Microsoft\Windows\CurrentVersion\Run").DeleteValue("keyNameForRegistry", false);

I believe these should work. I don't have time to test them now. There might be some typos. Dont forget to add, not sure if the both are needed tho.

using Microsoft.Win32;
using System.Reflection;