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Posted 12 Sep 2002

An ASP.NET thumbnail solution

An article describing a set of ASP.NET tools for generation of thumbnails and thumbnail views.
<%@ Control Language="C#" ClassName="ThumbList" Debug="true"%>
<%@ import Namespace="System.IO" %>
<%@ import Namespace="System.Drawing" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="PhilipSoft.Thumbnails" %>
<script runat="server">

    // ----- Copyright Philipos Sakellaropoulos 2002 -------
       private String _path,_vpath="", _filter="";
       private int _width,_height,_pagesize;
       private bool _bSaveThumbnails,_bShowFilenames;
       ThumbGenerator _oGenerator;
       // ------- public properties of the control ----------
       public int Width { get {return _width;} set {_width=value; } }
       public int Height { get {return _height;} set {_height=value; } }
       public String VPath { get {return _vpath;}
        set { _vpath=value.TrimEnd('/'); }
       }
       public int Columns
        { get {return MyThumbList.RepeatColumns;}
          set {MyThumbList.RepeatColumns=value; } }
       public String HeaderTitle;
       public bool SaveThumbnails
         { get {return _bSaveThumbnails;} set {_bSaveThumbnails=value; } }
       public bool ShowFilenames
         { get {return _bShowFilenames;} set {_bShowFilenames=value; } }
       // filter example: *.gif;*.jpg
       public String Filter { get {return _filter;} set { _filter=value; } }
       // im bored of get and set, i 'll make the rest public !!
       public bool AllowStretch;
       public bool AllowPaging;
       public bool HideNavBar;
       public bool Sort;
       public bool Refresh;
       public int PageSize
         { get {return _pagesize;}
         set {_pagesize=Math.Abs(value); } }
       public int CurPage;
       // by default don't use COM object unless explicitly requested
       public bool UseCOMobj;
       // create bevel effect for thumbnails
       public bool Bevel;
       public Color ItemBackColor
         { get { return MyThumbList.ItemStyle.BackColor; } set { MyThumbList.ItemStyle.BackColor=value; } }
       // new properties
       public bool ShowComments;
       public bool AllowEdit;
       
    // ~~~~~~~~~~~~~ Standard functions ~~~~~~~~~~~~~~~~~~~~~~~~~~~
       void Page_Load(Object Src, EventArgs e)
       {
        // get physical path of images
        _path = Server.MapPath(_vpath);
        
        // register client script to got to a next page
         StringBuilder scriptb = new StringBuilder();
         scriptb.Append("<script language=\"javascript\">\n");
         scriptb.Append("//<!--\n function GoToPage(vpath,n) { \n");
         scriptb.AppendFormat("document._ctl0.{0}.value=n; \n",hdnCurPage.ClientID);
         scriptb.Append(Page.GetPostBackEventReference(this));
         scriptb.Append("\n } \n//-->\n </");
         scriptb.Append("script>");
   
         if(!Page.IsClientScriptBlockRegistered("clientGotoPageScript"))
            Page.RegisterClientScriptBlock("clientGotoPageScript", scriptb.ToString());

         // if not in update, bind every time since parameters may have change
         if(MyThumbList.EditItemIndex < 0)
           BindThumbList();
       }
       
   // we are databound, now we know how many pages we have
    // and the current page so we can create the navigation bar
    void Item_DataBound(Object sender, DataListItemEventArgs e)
    {
      if(e.Item.ItemType == ListItemType.Footer) {
       Trace.Warn("DataBound event for footer");
       PlaceHolder plLinks = (PlaceHolder)e.Item.FindControl("plLinks");
       if(AllowPaging && !HideNavBar) CreateNavBar(plLinks);
       hdnPrevPath.Value = VPath;
      }
    }
       void ThumbList_EditCommand(Object sender, DataListCommandEventArgs e) 
      {
         MyThumbList.EditItemIndex = (int)e.Item.ItemIndex;
         BindThumbList();
      }

      void ThumbList_CancelCommand(Object sender, DataListCommandEventArgs e) 
      {
         MyThumbList.EditItemIndex = -1;
         BindThumbList();
      }

      void ThumbList_UpdateCommand(Object sender, DataListCommandEventArgs e) 
      {
         DataRowView drvTarget; 
         String sComment = (String)((TextBox)e.Item.FindControl("txtComment")).Text;
         String sFilename = ((TextBox)e.Item.FindControl("txtFilename")).Text; 
         
         DataSet dsComments = ReadCommentsFromXML();
     	 DataView dvCommentsFromXML = dsComments.Tables[0].DefaultView;
     	 dvCommentsFromXML.RowFilter =  "Filename='"+sFilename+"'";
     	 // find row for filename or create a new one if does not exist
     	 if (dvCommentsFromXML.Count > 0) { 
     	   drvTarget = dvCommentsFromXML[0];
     	   dvCommentsFromXML.RowFilter = "";
     	 }
     	 else {
     	   drvTarget = dvCommentsFromXML.AddNew();
     	   drvTarget[0] = sFilename;
     	 }
        drvTarget[1] = sComment;
        drvTarget.EndEdit();
   
        dsComments.WriteXml(_path +"\\ThumbComments.xml");
        
        MyThumbList.EditItemIndex = -1;
        BindThumbList();
      }
        
  // ~~~~~~~~~~~~~~ Custom Functions ~~~~~~~~~~~~~~~~~~~~~~~~~~~    
      public void BindThumbList()
      {
      String[] files; int i;
      ArrayList arFilesAll = new ArrayList();
      try {
      if(_filter.Length==0 || _filter=="*.*") {
        files = Directory.GetFiles(_path);
        arFilesAll.AddRange(files);
      }
      else { // separate different filters with ';'
        String[] filters = _filter.Split(';');
        for(i=0; i<filters.Length; i++) {
          files = Directory.GetFiles(_path,filters[i]);
          arFilesAll.AddRange(files);
        }
      }
      // create the datasource (list of files)
      for(i=0; i<arFilesAll.Count; i++)
        arFilesAll[i] = Path.GetFileName((String)arFilesAll[i]);
      MyThumbList.Attributes["TotalFiles"] = arFilesAll.Count.ToString();
      if(_bSaveThumbnails) {
        _oGenerator = new ThumbGenerator();
        String pathThumbs = _path+"\\thumbnails";
        Directory.CreateDirectory(pathThumbs);
        } // end if save thumbs
      } catch(Exception exDir) { arFilesAll = new ArrayList(); }
      // sort file-list if requested
      if(Sort)
        arFilesAll.Sort();
        
      // page thumblist if requested
      ArrayList arFilesToShow;
      if(!AllowPaging)
         arFilesToShow = arFilesAll;
      else { // create a data source with only the page files
       int totalPages = (int)Math.Ceiling((float)arFilesAll.Count/PageSize);
       if(totalPages==0) totalPages=1;
       MyThumbList.Attributes["TotalPages"] = totalPages.ToString();
       if(CurPage<1) {
         // we have not given a page from caller, get it from hidden field
         try {
          CurPage = int.Parse(hdnCurPage.Value); //Request.Form["__EVENTARGUMENT"]);
         } catch(Exception exParse) { CurPage=1; }
        }
       if(hdnPrevPath.Value!=VPath) // restart page numbering
         CurPage = 1;
       Trace.Warn("BindThumbList: Current page=" + CurPage.ToString());
       // make sure current page is in the [1,totalPages] range
       if(CurPage>totalPages) CurPage=totalPages;
       else if(CurPage<1) CurPage=1;
       // store curPage in attributes and in hidden field
       MyThumbList.Attributes["CurPage"] = CurPage.ToString();
       hdnCurPage.Value = CurPage.ToString();
       // put files of the page in the dsPageFiles array
       int startIndex = (CurPage-1)*PageSize;
       int endIndex = Math.Min(CurPage*PageSize,arFilesAll.Count);
       arFilesToShow = arFilesAll.GetRange(startIndex, endIndex-startIndex );
      } // end define page

 
       // create in-memory DataTable to be the data source
      DataTable dtThumbs = CreateCommentsTable();
      DataView dvCommentsFromXML = null;
      if(ShowComments || AllowEdit) {
        DataSet dsComments = ReadCommentsFromXML();
        dvCommentsFromXML = dsComments.Tables[0].DefaultView;
      }
      // add rows with filenames
      for(i=0; i<arFilesToShow.Count; i++) {
        // Response.Write(arFilesToShow[i]);
        DataRow dr = dtThumbs.NewRow();
        dr[0] = arFilesToShow[i];
	dtThumbs.Rows.Add(dr);
      } // next file
      // add existing comments
      if((ShowComments || AllowEdit) && dvCommentsFromXML!=null) {
	for(i = 0; i < dvCommentsFromXML.Count; i++) {
	  String sFilename=((String)dvCommentsFromXML[i][0]).Trim();
          DataRow[] foundRows = dtThumbs.Select("Filename = '"+sFilename+"'");
          if(foundRows.Length>0) 
            foundRows[0][1] = dvCommentsFromXML[i][1]; // copy comment
 	}
      }
 
      MyThumbList.DataSource = dtThumbs.DefaultView;
      MyThumbList.DataBind();
      } // end method
    
    
     private void CreateNavBar(PlaceHolder plLinks)
     {
      Trace.Warn("CreateNavBar()");
      CurPage = int.Parse(MyThumbList.Attributes["CurPage"]);
      int totalPages = int.Parse(MyThumbList.Attributes["TotalPages"]);
      if(totalPages == 1) return;
    
      //  --- i found a better solution with client script, see below
      //  LinkButton lbtPrev = new LinkButton();
      //  lbtPrev.Text="<< Prev"; lbtPrev.CommandName="Prev";
      //  lbtPrev.Command += new CommandEventHandler(LinkButton_Command);
      //  plLinks.Controls.Add(lbtPrev);
    
      // put the path also into the page links to change link status
      // (visited or not) when we change the virtual path
      if(CurPage>1) {
      // GoToPage client script updates hidden field with target page
      // and then causes a postback
        plLinks.Controls.Add(new LiteralControl(String.Format(
          "<A href=\"javascript:GoToPage('{0}',{1});\">&lt;&lt; Prev</A>&nbsp;&nbsp;",
          VPath,CurPage-1 )));
      }
      for(int i=1; i<=totalPages; i++) {
        String si = i.ToString();
        plLinks.Controls.Add(new LiteralControl("&nbsp;"));
        if(i==CurPage) {
          Label lblPage = new Label();
          lblPage.Text = si; lblPage.Font.Bold = true;
          plLinks.Controls.Add(lblPage);
        }
        else {
        plLinks.Controls.Add(new LiteralControl(String.Format(
          "<A href=\"javascript:GoToPage('{0}',{1});\">{2}</A>",
          VPath,si,si)));
       }
       if(i%10==0)
         plLinks.Controls.Add(new LiteralControl("<br/>"));
      } // next i
      if(CurPage<totalPages) {
        plLinks.Controls.Add(new LiteralControl(String.Format(
          "&nbsp;&nbsp;<A href=\"javascript:GoToPage('{0}',{1});\">Next &gt;&gt;</A>",
          VPath,CurPage+1)));
      }
     }

  DataSet ReadCommentsFromXML() {
    DataSet dsComments = new DataSet("ThumbnailDataset");
    // read comments from XML file 
    try {
       dsComments.ReadXml(_path +"\\ThumbComments.xml");
    } catch(Exception exRead) { }
    if(dsComments.Tables.Count==0) 
      dsComments.Tables.Add(CreateCommentsTable());
    return dsComments;
   }

  DataTable CreateCommentsTable() {
   DataTable dtThumbs = new DataTable("ThumbComment");  
   DataColumn dcPrimary = new DataColumn("Filename", typeof(string));
   dtThumbs.Columns.Add(dcPrimary);
   dtThumbs.Columns.Add(new DataColumn("Comment", typeof(string)));
   dtThumbs.PrimaryKey = new DataColumn[] { dcPrimary };
   dtThumbs.CaseSensitive = false;
   return dtThumbs;
   }

    
     // test function - not used
     void LinkButton_Command(Object sender, CommandEventArgs e)
     {
       Trace.Warn("You chose: " + e.CommandName + " Item " + e.CommandArgument);
     }
    
       String NumImagesDisplayed() {
         String sNum=((ICollection)MyThumbList.DataSource).Count.ToString();
         if(AllowPaging) sNum+= " of " + MyThumbList.Attributes["TotalFiles"];
         sNum += " images";
         if(AllowPaging) {
           sNum += String.Format(" (Page {0} of {1})",
            MyThumbList.Attributes["CurPage"],
            MyThumbList.Attributes["TotalPages"]);
         }
         return sNum;
       }
    
       // construct url of thumbnail
       String ThumbUrl(String sFile)
       {
         // if we use saved thumbnails, we must check if the file exists
         // if not we must create it using the oGenerator object
         if(_bSaveThumbnails) {
           _oGenerator.SetParams(String.Format("{0}\\{1}",_path,sFile),
            _width,_height,AllowStretch,Bevel,UseCOMobj);
           String sNameToSave = _oGenerator.GetUniqueThumbName();
           String sPathThumbFile=String.Format("{0}\\thumbnails\\{1}",
               _path,sNameToSave);
           if(!File.Exists(sPathThumbFile)) {
               try {
                Bitmap bmThumb = _oGenerator.ExtractThumbnail();
               _oGenerator.SaveThumbnail(bmThumb,sPathThumbFile);
               } catch (Exception exSave) { }
           } // if not exists
          return String.Format("{0}/thumbnails/{1}",_vpath,sNameToSave);
         }
         else { // create thumbnail in memory using the HTTP handler
          StringBuilder thurl = new StringBuilder();
          thurl.AppendFormat("{0}/ThumbJpeg.ashx?VFilePath={1}/{2}",
            TemplateSourceDirectory,_vpath,sFile);
          if(_width>0)  thurl.AppendFormat("&Width={0}",_width);
          if(_height>0)  thurl.AppendFormat("&Height={0}",_height);
          if(AllowStretch) thurl.Append("&AllowStretch=true");
          if(Bevel) thurl.Append("&Bevel=true");
          if(UseCOMobj) thurl.Append("&UseCOMobj=true");
          if(Refresh) thurl.Append("&Refresh=true");
          return thurl.ToString();
        }
       }
       
       String AltString(String sFile)
       {
       	 FileInfo fi = new FileInfo(String.Format("{0}\\{1}",_path,sFile));
	 long FileSize = fi.Length;
         return "Name: " + sFile + "&#10;&#13;Size: " + FileSize/1024 + " Kb";
       }
       
</script>
<!-------------------- Controls content here ------------------------------------->
<ASP:DataList id="MyThumbList" RepeatDirection="Horizontal" RepeatColumns="4" CellSpacing="3" runat="server" EnableViewState="true" OnItemDataBound="Item_DataBound"
 OnEditCommand="ThumbList_EditCommand" OnUpdateCommand="ThumbList_UpdateCommand"
 OnCancelCommand="ThumbList_CancelCommand"
>
    <ItemStyle font-size="8pt" horizontalalign="Center" borderwidth="1px" borderstyle="Solid" backcolor="White"></ItemStyle>
    <FooterStyle font-size="8pt" horizontalalign="Center" backcolor="#FFFFC0"></FooterStyle>
    <HeaderStyle font-size="11pt" font-bold="True" horizontalalign="Center"></HeaderStyle>
    <SelectedItemStyle backcolor="#E0E0E0"></SelectedItemStyle>
    <EditItemStyle borderwidth="1px" borderstyle="Groove"></EditItemStyle>
    <ItemTemplate>
        <a href="<%# String.Format("{0}/{1}",_vpath,
         ((DataRowView)Container.DataItem)["Filename"]) %>" > 
        <img border="0" src="<%# ThumbUrl((String)((DataRowView)Container.DataItem)["Filename"]) %>"
        alt="<%# AltString((String)((DataRowView)Container.DataItem)["Filename"]) %>" /></a>
        <%# _bShowFilenames?"<br/>"+((DataRowView)Container.DataItem)["Filename"]:"" %>
        <%# ShowComments?"<br/>"+((DataRowView)Container.DataItem)["Comment"]:"" %>
        <br/><asp:LinkButton id="button1" Visible='<%# AllowEdit ? true:false %>' 
           Text="Edit" CommandName="Edit" runat="server"/>
    </ItemTemplate>

    <EditItemTemplate>
        <a href="<%# String.Format("{0}/{1}",_vpath,
         ((DataRowView)Container.DataItem)["Filename"]) %>" > 
        <img border="0" src="<%# ThumbUrl((String)((DataRowView)Container.DataItem)["Filename"]) %>"
        alt="<%# AltString((String)((DataRowView)Container.DataItem)["Filename"]) %>" /></a> 
        <%# _bShowFilenames?"<br/>"+((DataRowView)Container.DataItem)["Filename"]:"" %>
        <ASP:TextBox id="txtFilename" Visible='false' 
          Text='<%# ((DataRowView)Container.DataItem)["Filename"] %>' runat="server"/>
        <br/><ASP:TextBox id="txtComment" Multiline='true' size='30' Rows='4' TextMode="MultiLine"
           Text='<%# ((DataRowView)Container.DataItem)["Comment"] %>' runat="server"/>
        <br/><asp:LinkButton id="button2" Text="Save" CommandName="Update" runat="server"/>
        &nbsp;<asp:LinkButton id="button3" Text="Cancel" CommandName="Cancel" runat="server"/>
    </EditItemTemplate>

    <HeaderTemplate>
        <%# HeaderTitle %> 
    </HeaderTemplate>
    <FooterTemplate>
        <%# NumImagesDisplayed() %> 
        <tr style="font-size: 8pt;" align="center">
            <td colspan=<%# Columns %>
                > 
                <p >
                    <asp:PlaceHolder id="plLinks" runat="server"></asp:PlaceHolder>
                </p>
            </td>
        </tr>
    </FooterTemplate>
</ASP:DataList>
<input id="hdnCurPage" type="hidden" runat="server" />
<input id="hdnPrevPath" type="hidden" runat="server" />

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This article, along with any associated source code and files, is licensed under Microsoft Reciprocal License

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About the Author

Philipos Sakellaropoulos
Web Developer Forthnet
Greece Greece
Software developer and Microsoft Trainer, Athens, Greece (MCT, MCSD.net, MCSE 2003, MCDBA 2000,MCTS, MCITP, MCIPD).

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Web02 | 2.8.180111.1 | Last Updated 11 Dec 2002
Article Copyright 2002 by Philipos Sakellaropoulos
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