Programmatically assign access control list (ACL) permission to 'this folder, subfolders and files'

I have to assign permission on a folder and it's child folder and files programmatically using C#.NET. I'm doing this as below:

var rootDic = @"C:\ROOT";
 var identity = "NETWORK SERVICE"; //The name of a user account.
 try
 {
     var accessRule = new FileSystemAccessRule(identity,
                          fileSystemRights: FileSystemRights.Modify,
                          inheritanceFlags: InheritanceFlags.ContainerInherit | InheritanceFlags.ObjectInherit,
                          propagationFlags: PropagationFlags.InheritOnly,
                          type: AccessControlType.Allow);
 
     var directoryInfo = new DirectoryInfo(rootDic);
 
     // Get a DirectorySecurity object that represents the current security settings.
     DirectorySecurity dSecurity = directoryInfo.GetAccessControl();
 
     // Add the FileSystemAccessRule to the security settings. 
     dSecurity.AddAccessRule(accessRule);
 
     // Set the new access settings.
     directoryInfo.SetAccessControl(dSecurity);
 }
 catch (Exception ex)
 {
     //...
 }
 

It does assign permission on my 'C:\ROOT' folder. But it assign permission to the Subfolders and Files only but not the 'ROOT' folder.

Q: How can I define the FileSystemAccessRule instance to assign permission to the ROOT folder, Subfolders and files?

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