The composite pattern and document composition

While representing part-whole hierarchies (tree-structured), the composite design pattern describes a group of objects to be treated in a uniform manner, as if the leaf node and interior nodes are instances of the same object. A document object can contain multiple tables, and we can nest tables as well. This is an instance of a part-whole hierarchy, and composite design pattern is a natural choice here. To create a composite, we need to declare a base class, and all objects should be derived from this base class:

    public abstract class TDocumentElement 
    { 
      public List<TDocumentElement> DocumentElements { get; set; } 
      //------ The method given below is for implementing Visitor     
      Pattern 
      public abstract void accept(IDocumentVisitor doc_vis); 
      //--- Code Omitted 
      public TDocumentElement() 
      { 
        DocumentElements = new List<TDocumentElement...