Display Hierarchical data with TreeView

TreeView Display Hierarchicaldata with Treeviewteemu Keiski


Very Oftenapplications have need to manage hierarchical data and indeed such-is thathierarchy. This is has been a bit problem in databases, althoughsolved using self-referencing tables or alternative solutions. OK, but how todisplay such the data that uses self-referencing table?



Withasp.net One optional answer is to use the TreeView control. TreeView givesdevelopers chance to display hierarchical data as I ' ll demonstrate in thisarticle. What makes TreeView So, it can also display elements (TreeNodes) based on XML.



Overview ofthings that developer needs to does to get this feature are:
Get the "Data from self-referencing table" into Datasetcreate DataRelation, corresponds to relation in self-referencing Table and add it to DataSet ' s Relations collection. DataRelation ' s Nested property needs to is true. Get DataSet ' s XML representation and apply XSLT transformation for it, so, corresponds to XML syntax used by Tre Eview control. Bind TreeView.

self-referencing table
Assume Thatin database We have table as follows:

CATEGORIES

CategoryID

Parentcategoryid

CategoryName

2



1

3



2

4



3

5

2

1.1

6

2

1.2

7

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

3.1.1.1.1

16

14

3.1.1.1.2

17

14

3.1.1.1.3



Shortly,categoryid is the primary key and Parentcategoryid are foreign key referencingto with default value NULL . CategoryName represents text I want todisplay in TreeView.


Get data into DataSet
Connection to Database

OleDbConnection objconn=newoledbconnection ("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=newoledbcommand ("SELECT * from CATEGORIES", objconn);



OleDbDataAdapter

OleDbDataAdapter Objda =newoledbdataadapter (objcommand);



DataSet

DataSet ds=newdataset ("CategoriesDS");



Fill DataSet

Objda.fill (ds, "CATEGORIES");


Nested DataRelation
Create DataRelation

DataRelation drel=newdatarelation ("categories_recursive"),
Ds. tables["CATEGORIES"]. Columns["CategoryID"],
Ds. tables["CATEGORIES"]. columns["Parentcategoryid"]);



Make sure relation is nested

Drel. Nested =true;



Add relation to DataSet ' s Relations collection

Ds. Relations.Add (Drel);


DataSet ' s XML and xslttransformation [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 ();



Load XSLT stylesheet

Objxsl.load (Server.MapPath ("transformationtemplate.xslt"));



StringWriter to temporarily hold of thetransformation

StringWriter writer=new StringWriter ();



Apply transformation with no arguments and dumpresults to StringWriter.

Objxsl.transform (Objdoc.createnavigator (), null,writer);


Bind TreeView [Result of transformation]
Set TreeView ' s treenodesrc property to get XML fromstringwriter.

Treeview1.treenodesrc =writer. ToString ();



Bind TreeView

Treeview1.databind ();



Close StringWriter

Writer. Close ();


Other useful aspalliance:
Programming with TreeView by Steve Sharrock
Developing with the Treeview Web control Part 1 by James Avery
Developing with the Treeview Web control Part 2 by James Avery