Check out example codes for "does Registry.CurrentUser.OpenSubKey create the key if it does not exist?". It will help you in understanding the concepts better.

Code Example 1

// No it does not - create it manually on null check
public void ConfigureWindowsRegistry()
{
    RegistryKey localMachine = RegistryKey.OpenBaseKey(Microsoft.Win32.RegistryHive.LocalMachine, RegistryView.Registry64); //here you specify where exactly you want your entry

   var reg = localMachine.OpenSubKey("Software\\Microsoft\\Office\\Outlook\\FormRegions\\tesssst",true);
   if (reg == null)
   {
       reg = localMachine.CreateSubKey("Software\\Microsoft\\Office\\Outlook\\FormRegions\\tesssst");
   }

   if (reg.GetValue("someKey") == null)
   {
       reg.SetValue("someKey", "someValue");
   }
}

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