RelatedPosts.cs :  » Bloggers » BlogEngine.NET » Controls » C# / CSharp Open Source

#region Using

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.IO;
using BlogEngine.Core;

#endregion

namespace Controls{

  public class RelatedPosts : Control
  {

    static RelatedPosts()
    {
      Post.Saved += new EventHandler<SavedEventArgs>(Post_Saved);
    }

    static void Post_Saved(object sender, SavedEventArgs e)
    {
      if (e.Action == SaveAction.Update)
      {
        Post post = (Post)sender;
        if (_Cache.ContainsKey(post.Id))
          _Cache.Remove(post.Id);
      }
    }

    #region Properties

    private IPublishable _Item;

    public IPublishable Item
    {
      get { return _Item; }
      set { _Item = value; }
    }

    private int _MaxResults = 3;

    public int MaxResults
    {
      get { return _MaxResults; }
      set { _MaxResults = value; }
    }

    private bool _ShowDescription;

    public bool ShowDescription
    {
      get { return _ShowDescription; }
      set { _ShowDescription = value; }
    }

    private int _DescriptionMaxLength = 100;

    public int DescriptionMaxLength
    {
      get { return _DescriptionMaxLength; }
      set { _DescriptionMaxLength = value; }
    }

    private string _Headline = Resources.labels.relatedPosts;

    public string Headline
    {
      get { return _Headline; }
      set { _Headline = value; }
    }

    #endregion

    #region Private fiels

    private static Dictionary<Guid, string> _Cache = new Dictionary<Guid, string>();
    private static object _SyncRoot = new object();

    #endregion

    /// <summary>
    /// Outputs server control content to a provided <see cref="T:System.Web.UI.HtmlTextWriter"></see> object and stores tracing information about the control if tracing is enabled.
    /// </summary>
    /// <param name="writer">The <see cref="T:System.Web.UI.HTmlTextWriter"></see> object that receives the control content.</param>
    public override void RenderControl(HtmlTextWriter writer)
    {
      if (!BlogSettings.Instance.EnableRelatedPosts || Item == null)
        return;

      if (!_Cache.ContainsKey(Item.Id))
      {
        lock (_SyncRoot)
        {
          if (!_Cache.ContainsKey(Item.Id))
          {
            List<IPublishable> relatedPosts = SearchForPosts();
            if (relatedPosts.Count <= 1)
              return;

            CreateList(relatedPosts);
          }
        }
      }

      writer.Write(_Cache[Item.Id].Replace("+++", this.Headline));
    }

    /// <summary>
    /// Creates the list of related posts in HTML.
    /// </summary>
    /// <param name="relatedPosts">The related posts.</param>
    private void CreateList(List<IPublishable> relatedPosts)
    {
      System.Text.StringBuilder sb = new System.Text.StringBuilder();

      string link = "<a href=\"{0}\">{1}</a>";
      string desc = "<span>{0}</span>";
      sb.Append("<div id=\"relatedPosts\">");
      sb.Append("<p>+++</p>");
      sb.Append("<div>");
      
      int count = 0;
      foreach (IPublishable post in relatedPosts)
      {
        if (post != this.Item)
        {
          sb.Append(string.Format(link, post.RelativeLink, HttpUtility.HtmlEncode(post.Title)));
          if (ShowDescription)
          {
            string description = post.Description;
            if (description != null && description.Length > DescriptionMaxLength)
              description = description.Substring(0, DescriptionMaxLength) + "...";

            if (String.IsNullOrEmpty(description))
            {
              string content = Utils.StripHtml(post.Content);
              description = content.Length > DescriptionMaxLength ? content.Substring(0, DescriptionMaxLength) + "..." : content;
            }

            sb.Append(string.Format(desc, description));
          }
          count++;
        }

        if (count == MaxResults)
          break;
      }

      sb.Append("</div>");
      sb.Append("</div>");
      _Cache.Add(Item.Id, sb.ToString());
    }

    private List<IPublishable> SearchForPosts()
    {
      return Search.FindRelatedItems(this.Item);
    }
  }
}