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?