ASP. net c # generate a drop-down list tree

: Code: [csharp] using System. data; using System. web. UI. webControls; // <summary> // generate a drop-down list tree based on the DataTable // </summary> public class DropDownListHelp {private string gridline; private DataTable dt; public DropDownListHelp () {// TODO: add the constructor logic here // <summary> // generate a tree-like drop-down menu based on the Datatable /// </summary> /// <param name = "datatable "> </param> /// <param name =" parentKeyField "> key field of the parent node </param> /// <para M name = "parentKey"> upper-level node value </param> /// <param name = "keyField"> key field of the current node </param> /// <param name = "sortString"> sort string </param> // <param name = "ddl"> DownList </param> public void createDropDownTree (DataTable datatable, string parentKeyField, string parentKey, string keyField, string textField, string sortString, DropDownList ddl) {dt = datatable; ddl. items. add (new ListItem ("", ""); addChildItems (parentKe YField, parentKey, keyField, textField, sortString, ddl );} /// <summary> /// recursively generated Tree node /// </summary> /// <param name = "parentKeyField"> key field of the parent node </param>/ // <param name = "parentKey"> upper-level node value </param> // <param name = "keyField"> key field of the current node </param> // <param name = "sortString"> sort string </param> // <param name = "ddl"> DownList Control </param> /// <returns> </returns> private void addChildItems (string parentKeyField, string ParentKey, string keyField, string textField, string sortString, DropDownList ddl) {DataView dv = new DataView (dt, parentKeyField + "= '" + parentKey + "'", sortString, DataViewRowState. currentRows); int a = dv. count; if (dv. count = 0) {return ;}for (int I = 0; I <a; I ++) {gridline = ""; dv. rowFilter = parentKeyField + "= '" + parentKey + "'"; dv. sort = sortString; getTreeLine (parentKeyField, Dv [I] [parentKeyField]. toString (), keyField, dv [I] [keyField]. toString (), sortString); dv. rowFilter = parentKeyField + "= '" + parentKey + "'"; dv. sort = sortString; ddl. items. add (new ListItem (gridline + (I = a-1? "Plaintext": "plaintext") + dv [I] [textField]. toString (), dv [I] [keyField]. toString (); addChildItems (parentKeyField, dv [I] [keyField]. toString (), keyField, textField, sortString, ddl);} dv. dispose ();} /// <summary> /// trace the connection line of the Spanning Tree /// </summary> /// <param name = "parentKeyField"> key field of the parent node </param> /// <param name = "parentKey"> upper-level node value </param> /// <param name = "keyField"> key field of the current node </param> /// <param name = "nodeKey"> current node value </param> /// <param name = "sortString"> sort string </param> /// <returns> </ returns> private void getTreeLine (string parentKeyField, string parentKey, string keyField, string nodeKey, string sortString) {// select the parent node DataView dv = new DataView (dt, keyField + "= '" + parentKey + "'", sortString, DataViewRowState. currentRows); if (dv. count> 0) {// select the same level node dv of the parent node. rowFilter = parentKeyField + "= '" + dv [0] [parentKeyField]. toString () + "'"; dv. sort = sortString; for (int j = 0; j <dv. count; j ++) {if (dv [j] [keyField]. toString () = parentKey) {if (j = dv. count-1) {gridline = "" + gridline;} else {gridline = "break" + gridline ;}} getTreeLine (parentKeyField, dv [0] [parentKeyField]. toString (), keyField, dv [0] [keyField]. toString (), sortString);} dv. dispose () ;}} call: [csharp] DropDownListHelp ddlHelper = new DropDownListHelp (); ddlHelper. createDropDownTree (dt, "parentID", "1", "ID", "Text", "Text asc", DropDownList1 );