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Posted 16 Sep 2007
Licenced CPOL

Tree Chart Generator

, 18 Nov 2007
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An article on the development of a Tree Chart Generator


There is, in organizations, a constant need to display tree structures. This can be done for file systems, Organization charts, Bill of Material, etc. This article discusses a component which can generate an image of the required tree, based on the data in a DataTable. The DLL can be called from Windows Forms or ASP.NET. Most of the parameters (sizes, colors) can be controlled by the developer using the DLL; they are exposed as properties.

This first version of this DLL was called OrgChart Generator and was published here. During development of a BOM display application, it became obvious that the Org chart Generator lacks a few very important issues:

  1. It was too specific: the DLL is a Tree generator and should be named as such.
  2. A node in the Tree could not appear twice. An Employee may work for more than one department.
  3. The data structure used (both an XmlDocument and a SortedDictionary) was not good enough.

So, it became necessary to rewrite the whole application and give it a new name. Hence, this article.

Using the Code

The download ZIP file contains the C# solution, which has two projects:

  1. TreeGenerator, which contains the code for the DLL that generates the Tree image
  2. TestTreeGenerator, which contains a Windows Forms application that demonstrates the abilities of TreeGenerator and its usage.


The TreeGenerator accepts a Typed DataTable in the constructor, with the node list, in order to generate the tree. The TreeData.TreeDataTableDataTable is the DataTable that the class will accept in the constructor. It can contain the whole tree structure or just parts of it. If it contains the whole tree, multiple miniTrees can be created from the same instance of the object. The structure of the DataTable is as follows:

  • string nodeID - Primary Key - the ID of the node - employee number, item code or anything else that uniquely identifies the node
  • string parentNodeID - Primary Key - The ID of the node parent. This defines the tree structure. It may be String.Empty
  • string nodeDescription - A short description for the node
  • string nodeNote - A note for the node


There is just one main method, GenerateTree, which is overloaded. The difference between the overloads is that one method accepts as parameters the required size of the resulting image and resizes it before returning it. The other returns it in the size as determined by calculation - the number of boxes (both x & y) times the number of nodes.
This method returns a System.IO.Stream , which can be used to display an image, save to file, or any other activity. Another important parameter for this method is the StartFromNodeID. This parameter determines which node will be at the top of the tree.

Another method exists mainly as a helper method. getRectangleFromNode is used internally, but can also be used externally to return the Rectangle of the node coordinates, based on the XmlNode. This class/DLL can be used from a Windows Forms application in the following way:

//First - create the DataTable. In real life it would be extracted from a DB
//or created some other way. 
private void Form1_Load(object sender, EventArgs e) {
            TreeGenerator.TreeData.TreeDataTableDataTable dtTree = 
			new TreeData.TreeDataTableDataTable(); 
            dtTree.AddTreeDataTableRow("1000", "","1000",""); 
            dtTree.AddTreeDataTableRow("2000", "1000","2000",""); 
            dtTree.AddTreeDataTableRow("2001", "1000","2001",""); 
            dtTree.AddTreeDataTableRow("3000","2000", "3000",""); 
            dtTree.AddTreeDataTableRow("3001", "2000", "3001",""); 
            dtTree.AddTreeDataTableRow("3000", "2001", "3000",""); 
            dtTree.AddTreeDataTableRow("4000", "3000", "4000",""); 
            dtTree.AddTreeDataTableRow("4001", "3000", "4001", ""); 
          //instantiate the object 
          myTree = new TreeBuilder(dtTree);    
        //Now - Generate the tree itself
        picTree.Image = Image.FromStream(


The image that is returned has default properties. In order to control the sizes and colors of the Tree, these properties can be changed (all sizes are in pixels):

  • BoxFillColor - Which color will fill the boxes
  • BoxWidth - The width of each box
  • BoxHeight - The height of each box
  • Margin - The margin from the edges of the image to the boxes
  • HorizontalSpace - The space between the 2 employee boxes on the same level
  • VerticalSpace - The space between 2 levels of employees
  • FontSize - The font size for the node details
  • LineColor - The color of both the box line and the connecting line
  • LineWidth - The width of both the box line and the connecting line
  • BGColor - The color in the Background of the image
  • FontColor - The font color
  • xmlTree - An XmlDocument containing all the tree data, including the position of each node on the chart. This can be used for checking if a specific node was clicked.

Changing these properties could generate weird results, so care should be taken by the user. For example, it would not look good if both the BoxFillColor and the FontColor were the same.

Trapping MouseClick Events

Using the xmlTree property, it can be determined where the user clicked. Below is an example for a Windows Forms application. This will not work for ASP.NET.

private void picOrgChart_MouseClick(object sender, MouseEventArgs e)
            Rectangle currentRect;
            //determine if the mouse clicked on a box, 
            //if so, show the node description.
            string SelectedNode = "No Node";
            //find the node
            foreach (XmlNode oNode in myTree.xmlTree.SelectNodes("//Node"))
                //iterate through all employees until found.
                currentRect = myTree.getRectangleFromNode(oNode);
                if (e.X >= currentRect.Left &&
                    e.X <= currentRect.Right &&
                    e.Y >= currentRect.Top &&
                    e.Y <= currentRect.Bottom)
                    SelectedNode = 


Using this code in ASP.NET requires two pages (see attached ZIP file):

  1. ShowTree.aspx - Accepts the user input and shows the image
  2. OrgChartImage.aspx - Generates the image and returns it to the calling page.


The page contains a textbox that accepts any input. Whatever the user typed will become the top node of the tree. In real life, the textbox (or DDL, or any other control) will accept only employee ID, Item Code, etc. Clicking on the "Show Tree" button will show the tree for the typed in name. In this case, it will be a randomly generated tree. In real life, the tree data should be selected from a database.

Clicking on any of the tree nodes will show the child nodes of that node, in a new tree. It is possible, instead of showing a new tree each time, to enlarge the tree all the time, by keeping the tree dataTable as a static object.

The main function in this page is the one that generates the image. The image can be shown as an imageMap, or any other image tag. In this case, the imageMap.ImageUrl is linked to the page which reads the image from the cache and returns it as a stream.
This function also gets the XmlDocument from the TreeGenerator object and defines the hotspots for the imageMap.

private void GenerateChart(string mItem) 
        //create the chart object 
        TreeGenerator.TreeBuilder currentBOM       
            = new TreeGenerator.TreeBuilder(GetDT(mItem));
        //specify visual properties
        currentBOM.HorizontalSpace = 15;
        currentBOM.VerticalSpace = 15;
        currentBOM.FontSize = 7;
        currentBOM.BoxHeight = 80;
        currentBOM.BoxWidth = 80;
        currentBOM.LineColor = 
        currentBOM.FontColor = 
           System.Drawing.Image OC = 
              mItem, System.Drawing.Imaging.ImageFormat.Bmp)); 
           string nameOfImage =
        Session.SessionID + "CurrentImage"; 
        //save in the cache, to be used by the page creating the image 
        Cache.Insert(nameOfImage, OC, null, 
           CacheItemPriority.NotRemovable, null); 
        //update the item image map 
        //supply the image name by querystring 
        impBOM.ImageUrl = "~/OrgChartImage.aspx?ID=" + nameOfImage;
        //remove all hotspots 
        //regenerate the hotspots. 
        foreach (XmlNode oNode in currentBOM.xmlTree.SelectNodes("//Node")) 
        RectangleHotSpot RectHS
            = new RectangleHotSpot();
            RectHS.HotSpotMode = HotSpotMode.PostBack; Rectangle
            currentRect = currentBOM.getRectangleFromNode(oNode);
            RectHS.Top = currentRect.Top;
            RectHS.Bottom = currentRect.Bottom;
            RectHS.Left = currentRect.Left;
            RectHS.Right = currentRect.Right;
            RectHS.PostBackValue = oNode.Attributes["nodeID"].InnerText;
              = oNode.Attributes["nodeDescription"].InnerText; 


This page loads the cache item based on the passed parameter, converts it into an image and writes it into the output stream. There is only one function here:

protected void Page_Load(object sender, EventArgs e)
        // Change the response headers to output a JPEG image.
        this.Response.ContentType = "image/jpeg";
        System.Drawing.Image OC = null;
        //Build the image 
        string imageName = Request.QueryString["ID"];
        if (Cache[imageName] != null)
            OC = (System.Drawing.Image)Cache[imageName];
            // Write the image to the response stream in JPEG format.
            OC.Save(this.Response.OutputStream, ImageFormat.Jpeg);


  • 16th September, 2007 - Initial release
  • 23rd September, 2007 - Added ASP.NET usage sample


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Rotem Sapir
Web Developer
Israel Israel
No Biography provided

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Comments and Discussions

GeneralImage not working on server Pin
avinash s27-Apr-11 2:25
memberavinash s27-Apr-11 2:25 
GeneralRe: Image not working on server Pin
kshitij_mehta10-Aug-11 18:01
memberkshitij_mehta10-Aug-11 18:01 
GeneralContact for more developement Pin
Gal9921-Apr-11 3:09
memberGal9921-Apr-11 3:09 
GeneralNeed help When child node is in same line of Parent Pin
Member 294169218-Jan-11 9:03
memberMember 294169218-Jan-11 9:03 
GeneralRe: Need help When child node is in same line of Parent Pin
Rotem Sapir23-Jan-11 21:52
memberRotem Sapir23-Jan-11 21:52 
GeneralError: Column 'nodeID, parentNodeID' is constrained to be unique. Pin
Murthy Pothukuchi18-Jan-11 3:18
memberMurthy Pothukuchi18-Jan-11 3:18 
GeneralRe: Error: Column 'nodeID, parentNodeID' is constrained to be unique. Pin
Rotem Sapir23-Jan-11 21:55
memberRotem Sapir23-Jan-11 21:55 
GeneralRe: Organization Chart Control for Winforms and ASP.NET Webforms - Free Pin
Rotem Sapir5-Dec-10 11:13
memberRotem Sapir5-Dec-10 11:13 
You're putting in a free ad to your product.
Not cool.
Please remove this.
GeneralOut of Memory Error - Exception Pin
ketan5411-Dec-10 17:47
memberketan5411-Dec-10 17:47 
GeneralRe: Out of Memory Error - Exception Pin
Rotem Sapir5-Dec-10 11:06
memberRotem Sapir5-Dec-10 11:06 
GeneralSystem.OutOfMemoryException Pin
ketan54129-Nov-10 21:59
memberketan54129-Nov-10 21:59 
GeneralI'm getting a red "X" only Pin
digidigi3323-Dec-09 7:38
memberdigidigi3323-Dec-09 7:38 
GeneralRe: I'm getting a red "X" only Pin
Rotem Sapir24-Dec-09 10:29
memberRotem Sapir24-Dec-09 10:29 
GeneralGreat Job Pin
www042815-Oct-09 3:32
memberwww042815-Oct-09 3:32 
GeneralRe: Great Job Pin
Rotem Sapir23-Oct-09 0:01
memberRotem Sapir23-Oct-09 0:01 
GeneralRe: Great Job [modified] Pin
cris033412-Nov-09 8:33
membercris033412-Nov-09 8:33 
GeneralRe: Great Job Pin
Rotem Sapir14-Nov-09 23:28
memberRotem Sapir14-Nov-09 23:28 
Generalset image width and height Pin
kieran540515-Jul-09 4:51
memberkieran540515-Jul-09 4:51 
GeneralRe: set image width and height Pin
Rotem Sapir23-Oct-09 0:00
memberRotem Sapir23-Oct-09 0:00 
GeneralThanx Pin
usmanmughal14-Jul-09 22:12
memberusmanmughal14-Jul-09 22:12 
GeneralRe: Thanx Pin
Rotem Sapir15-Jul-09 2:38
memberRotem Sapir15-Jul-09 2:38 
GeneralPlz help me Pin
usmanmughal11-Jul-09 0:50
memberusmanmughal11-Jul-09 0:50 
AnswerRe: Plz help me Pin
Rotem Sapir13-Jul-09 2:11
memberRotem Sapir13-Jul-09 2:11 
GeneralRe: error "Parameter is not valid" Pin
sfghk9-Mar-09 2:34
membersfghk9-Mar-09 2:34 
GeneralRe: error "Parameter is not valid" Pin
Rotem Sapir10-Mar-09 21:03
memberRotem Sapir10-Mar-09 21:03 

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