Three-Level linkage in ASP pages to load data

ASP page:

Card category: <asp: dropdownlist id = "dropdownlist_cardtype1" runat = "server" autopostback = "true" onselectedindexchanged = "inline" datatextfield = "typename" datavaluefield = "typenum"> </ASP: dropdownlist> <asp: dropdownlist id = "dropdownlist_cardtype2" runat = "server" autopostback = "true" onselectedindexchanged = "inline" datatextfield = "typename" datavaluefield = "typenum"> </ASP: dropdownlist> <asp: dropdownlist id = "dropdownlist_cardtype3" runat = "server" datatextfield = "typename" datavaluefield = "typenum"> </ASP: dropdownlist>

Set autopostback = "true" in the first and second drop-down boxes"

C # background code:

# Region _____________ load data _____ card type ____________ // card type string typesql = "select distinct typenum, typename from tbl_cardtypenew where typelevel = '1'"; dataset ds2 = dbfhkhelper. querydb (typesql); If (! Ispostback) {If (ds2.tables [0]. rows. count> 0) {datatable Table1 = new datatable (); table1.columns. add ("typenum"); table1.columns. add ("typename"); datarow drnew = table1.newrow (); drnew ["typename"] = "-All-"; drnew ["typenum"] = "-All -"; table1.rows. add (drnew); table1.merge (ds2.tables [0]); dropdownlist_cardtype1.datasource = Table1; dropdownlist_cardtype1.databind (); rows = 0 ;}// the second type of able Table2 = new datatable (); table2.columns. add ("typenum"); table2.columns. add ("typename"); datarow drnew2 = table2.newrow (); drnew2 ["typename"] = "-All-"; drnew2 ["typenum"] = "-All -"; table2.rows. add (drnew2); dropdownlist_cardtype2.datasource = Table2; dropdownlist_cardtype2.databind (); frequency = 0; // The third type: dropdownlist_cardtype3.datasource = Table2; frequency (); frequency = 0 ;} # endregion _____________ load data _________________

Select an event in the first drop-down box and load the data in the second drop-down box.

C # The Code is as follows:

# After region selects the level 1 category, load the Level 2 category protected void dropdownlist_cardtype1_selectedindexchanged (Object sender, eventargs e) {dropdownlist_cardtype2.datasource = NULL; dropdownlist_cardtype3.datasource = NULL; // able Table2 = new datatable (); table2.columns. add ("typenum"); table2.columns. add ("typename"); datarow drnew2 = table2.newrow (); drnew2 ["typename"] = "-All-"; drnew2 ["typenum"] = "-All -"; tabl E2.rows. Add (drnew2); dropdownlist_cardtype3.datasource = Table2; dropdownlist_cardtype3.databind (); bytes = 0; string type1 = bytes (); // 01-type name if (type1! = "-All-") {// query the second-level card category string querysql = "select typenum, typename from tbl_cardtypenew where uplnum = '"+ type1 +"' and typelevel = '2' "; dataset ds2 = dbfhkhelper. querydb (querysql); If (ds2.tables [0]. rows. count> 0) {datatable Table1 = new datatable (); table1.columns. add ("typenum"); table1.columns. add ("typename"); datarow drnew = table1.newrow (); drnew ["typename"] = "-All-"; drnew ["typenum"] = "-All -"; table1.rows. add (drnew); table1.merge (ds2.tables [0]); dropdownlist_cardtype2.datasource = Table1; dropdownlist_cardtype2.databind (); dropdownlist_cardtype2.selectedindex = 0 ;} else {// second-level card category datatable table3 = new datatable (); table3.columns. add ("typenum"); table3.columns. add ("typename"); datarow drnew3 = table3.newrow (); drnew3 ["typename"] = "-All-"; drnew3 ["typenum"] = "-All -"; table3.rows. add (drnew3); dropdownlist_cardtype2.datasource = table3; dropdownlist_cardtype2.databind (); Category = 0 ;}} else {// datatable table3 = new datatable (); table3.columns. add ("typenum"); table3.columns. add ("typename"); datarow drnew3 = table3.newrow (); drnew3 ["typename"] = "-All-"; drnew3 ["typenum"] = "-All -"; table3.rows. add (drnew3); dropdownlist_cardtype2.datasource = table3; dropdownlist_cardtype2.databind (); dropdownlist_cardtype2.selectedindex = 0 ;}# endregion select the level 1 category and load the Level 2 Category

Select an event in the second drop-down box and load the data in the third drop-down box:

# After region selects the second-level card category, load the third-level card category protected void dropdownlist_cardtype2_selectedindexchanged (Object sender, eventargs e) {dropdownlist_cardtype3.datasource = NULL; string type2 = callback (); // 0102-type name if (type2! = "-All-") {// query the string querysql = "select typenum, typename from tbl_cardtypenew where uplnum = '"+ type2 +"' and typelevel = '3' "; dataset ds2 = dbfhkhelper. querydb (querysql); If (ds2.tables [0]. rows. count> 0) {datatable Table1 = new datatable (); table1.columns. add ("typenum"); table1.columns. add ("typename"); datarow drnew = table1.newrow (); drnew ["typename"] = "-All-"; drnew ["typenum"] = "-All -"; table1.rows. add (drnew); table1.merge (ds2.tables [0]); dropdownlist_cardtype3.datasource = Table1; dropdownlist_cardtype3.databind (); dropdownlist_cardtype3.selectedindex = 0 ;} else {// third-level card category datatable table3 = new datatable (); table3.columns. add ("typenum"); table3.columns. add ("typename"); datarow drnew3 = table3.newrow (); drnew3 ["typename"] = "-All-"; drnew3 ["typenum"] = "-All -"; table3.rows. add (drnew3); dropdownlist_cardtype3.datasource = table3; dropdownlist_cardtype3.databind (); Category = 0 ;}} else {// able table3 = new datatable (); table3.columns. add ("typenum"); table3.columns. add ("typename"); datarow drnew3 = table3.newrow (); drnew3 ["typename"] = "-All-"; drnew3 ["typenum"] = "-All -"; table3.rows. add (drnew3); dropdownlist_cardtype3.datasource = table3; dropdownlist_cardtype3.databind (); dropdownlist_cardtype3.selectedindex = 0 ;}# endregion select Level 2 Category and load level 3 Category