Display Hierarchical Data with TreeView
TEEMU Keiski
Very often applications have need to manage hierarchical data and indeed such that hierarchy is unlimited. This has been a bit problem in databases, although solved using self-referencing tables or alternative solutions. OK, but how to display such data that uses self-referencing TABLE?
With ASP.NET one optional answer is to use TreeView control. TreeView gives developers chance to display hierarchical data as I'll demonstrate in this article. What makes TreeView so cool is that it can also display elements (tree nodes) based on XML.
Overview of things that developer Needs to do to get this Feature Are:
Get The Data from Self-Referencing Table Into DataSet
Create DataRelation That Corresponds To RELATION IN Self-Referencing Table and add it to DataSet's Relations Collection. DataRelation's Nested Property Needs to be true.
Get DataSet's XML Representation and Apply Xslt Transformation For It So That Result Corresponds to Xml Syntax Used by TreeView Control.
Bind TreeView.
Self-Referencing Table
Assume That In Database We Have Table as Follows:
Categories
CategoryID
ParentcategoryID
CategoryName
2
1 3
twenty four
3 5 2 1.3 8 3 2.1 9 3 2.2 10 4 3.1 11 5 1.1.1 12 5 1.1.2 13 10 3.1.1 14 13 3.1.1.1 15 14 3.1.1.1.11 16 14 3.1. 1.1.2 17 14 3.1.1.1.3
Shortly, categoryid is the primary key and petcategoryid is foreign key referencing to categoryid with default value null. CategoryName Represents text i Want To Display In TreeView.
Get Data Into DataSet
// Connection to Database
OLEDBCONNECTION OBJCONN = New OLEDBCONNECTION ("provider = microsoft.jet.OleDb.4.0; data source =" server.mappath ("db.mdb") "; persist security info = false"); // SQL Query to get Data From categories table
OLEDBCommand objcommand = new oledbcommand ("Select * from categories", objconn;
// OLEDBDataAdapter
OLEDBDataAdapter objda = new oledbdataadapter (Objcommand);
// dataset
Dataset DS = New Dataset ("CategoriesDS");
// Fill DataSet
Objda.Fill (DS, "categories");
Nested DataRelation
// CREATE DATARELATION
Dataralation Drel = New DataRelation ("categories_recursive", ds.tables ["categories"]. Columns ["categoryid"], ds.tables ["categories"]. Column ["parentcategoryID"]);
// Make Sure Relation IS NESTED
Drel.NESTED = TRUE;
// Add rate to DataSet's Relations Collection
DS.RELATIONS.ADD (DREL);
DataSet's XML and Xslt Transformation [Source XML] [xslt stylesheet]
// xmldocument to hold xml generated from dataset
XMLDocument Objdoc = new xmldocument ();
// load XML
Objdoc.loadxml (DS.GETXML ());
// CREATE XSLTRANSFORM OBJECT
Xsltransform objxsl = new xsltransform ();
// loading xslt stylesheet
Objxsl.Load (Server.Mappath ("TransformationTemplate.xslt");
// StringWriter to Temporarily Hold Result of the Transformation
StringWriter Writer = new stringwriter ();
// Apply Transformation with no arguments and dump results to stringwriter.
Objxsl.Transform (Objdoc.createnavigator (), null, write);
Bind TreeView [Result of Transformation]
// set Treeview's Treenodesrc property to get XML from stringwriter.
TreeView1.treenodesrc = Writer.toString ();
// Bind TreeView
TreeView1.databind ();
// close stringwriterwriter.close ();
Other Useful Resources at Aspalliance:
Programming with treeview by Steve Sharock
Developing with the treeview Web Control Part 1 by James Avery
Developing with the treeview web control part 2 by James avery
