List as ICollection

 
  // Empty
  public bool IsEmpty()
  {
    return first == null;
  }
 
  // Add is simply "AddF", slightly revisited.
  public void Add(T value)
  {
    if (isReadonly)
    {
      throw new InvalidOperationException(
        "List is read-only."
      );
    }
    Cell cCell = first;
    if (cCell != null)
    {
      while (cCell.Next != null)
      // As long as the cCell Cell has a neighbour…
      {
        cCell = cCell.Next;
        // We move the cCell cell to this neighbour.
      }
      cCell.Next = new Cell(value, null);
    }
    else
    {
      first = new Cell(value, null);
    }
  }
 
  public void Clear()
  {
    first = null;
  }
 
  public bool Contains(T value)
  {
    bool found = false;
    Cell cCell = first;
    while (cCell != null && !found)
    {
      if (cCell.Data.Equals(value))
      {
        found = true;
      }
      cCell = cCell.Next;
    }
    return found;
  }
 
  // Copies the elements of the ICollection to an Array, starting at a particular Array index.
  public void CopyTo(T[] array, int arrayIndex)
  {
    if (array == null)
      throw new ArgumentNullException(
        "The array cannot be null."
      );
    if (arrayIndex < 0)
      throw new ArgumentOutOfRangeException(
        "The starting array index cannot be negative."
      );
    if (Count > array.Length - arrayIndex)
      throw new ArgumentException(
        "The destination array has fewer elements than the collection."
      );
 
    Cell cCell = first;
    int i = 0; // keeping track of how many elements were copied.
    while (cCell != null)
    {
      array[i + arrayIndex] = cCell.Data;
      i++;
      cCell = cCell.Next;
    }
  }
 
  public bool Remove(T value)
  {
    if (isReadonly)
    {
      throw new InvalidOperationException(
        "List is read-only"
      );
    }
    bool removed = false;
    if (!IsEmpty())
    {
      if (first.Data.Equals(value))
      {
        first = first.Next;
        removed = true;
      }
      else
      {
        Cell cCell = first;
        while (cCell.Next != null)
        {
          if (cCell.Next.Data.Equals(value))
          {
            cCell.Next = cCell.Next.Next;
            removed = true;
          }
        }
      }
    }
    return removed;
  }
 
  public int Count
  {
    get
    {
      int size = 0;
      Cell cCell = first;
      while (cCell != null)
      {
        cCell = cCell.Next;
        size++;
      }
      return size;
    }
  }
 
  public bool isReadonly = false;
  public bool IsReadOnly
  {
    get { return isReadonly; }
    set { isReadonly = value; }
  }
 
  public IEnumerator<T> GetEnumerator()
  {
    Cell cCell = first;
    while (cCell != null)
    {
      yield return cCell.Data;
      cCell = cCell.Next;
    }
  }
 
  IEnumerator IEnumerable.GetEnumerator()
  {
    return this.GetEnumerator(); // call the generic version of the method
  }