How to set null object A in List<A>() C#

[Rushabh Verma]

I have a class A like this:

public class Article
{
public Tag Test1 { get; set; } = new Tag();

}

public class Tag
{
public List<News> Test{ get; set; } = new List<News>();
}

I have a list like this:

News 1
   Tag 1{
             News 1
                   **Tag** {
                           News 1
                                Tag {....}
                           News 4
                                Tag {....}
                           News 5
                                Tag {....}
                       }
             News 4
                   Tag {....}
             News 5
                   Tag {....}
         }
News 2
News 3

I want to set null "Tag" 2nd on that list = null to avoid loop infinitely. like this:

News 1
   Tag 1{
             News 1
                   Tag = null
             News 4
                   Tag = null
             News 5
                   Tag = null
          }
News 2
News 3