Composite_FileDirEntry.cs

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using System;
using System.Collections.Generic;
 
namespace DesignPatternExamples_csharp
{
    public enum FileDirTypes
    {
        File,
 
        Directory
    }
 
 
    public class FileDirEntry
    {
        public virtual FileDirTypes FileDirType
        {
            get;
            protected set;
        }
 
        public virtual string Name
        {
            get;
            protected set;
        }
 
        public virtual long Length
        {
            get;
            protected set;
        }
 
        public virtual DateTime WhenModified
        {
            get;
            protected set;
        }
 
        public virtual FileDirEntry[]? Children
        {
            get
            {
                return null;
            }
        }
 
        public FileDirEntry()
        {
            FileDirType = FileDirTypes.File;
            Name = string.Empty;
            Length = 0;
            WhenModified = DateTime.MinValue;
        }
 
    }
 
 
    //########################################################################
    //########################################################################
 
 
    class FileEntry : FileDirEntry
    {
        public FileEntry(string name, long size, DateTime modDate)
        {
            FileDirType = FileDirTypes.File;
            Name = name;
            Length = size;
            WhenModified = modDate;
        }
    }
 
 
    //########################################################################
    //########################################################################
 
 
    class DirEntry : FileDirEntry
    {
        List<FileDirEntry> _children;
        long _length;
        bool _lengthSet;
 
        public DirEntry(string name, DateTime modDate, FileDirEntry[] children)
        {
            if (children == null)
            {
                throw new ArgumentNullException("children", "The list of children cannot be null but can be empty.");
            }
            FileDirType = FileDirTypes.Directory;
            Name = name;
            WhenModified = modDate;
            _children = new List<FileDirEntry>(children);
        }
 
 
        public override long Length
        {
            get
            {
                if (!_lengthSet)
                {
                    // Recurse over all children, accumulating their size.
                    foreach(FileDirEntry entry in Children)
                    {
                        _length += entry.Length;
                    }
                    _lengthSet = true;
                }
                return _length;
            }
        }
 
 
        public override FileDirEntry[] Children
        {
            get
            {
                return _children.ToArray();
            }
        }
    }
}