asp.net - Fill Dropdown in asp dotnet from Caching -

i have dropdown in asp.net fills agent list. agent list 30,000. want keep data in cache dont need fill dropdown again , again database. how achieve caching. please guide

suppose have cache varriable, have convert datatable,

datatable tblcategories = (datatable) cache["categories"]; 

and , check, if still datatable empty, fetch database using loadcategoryindropdownlist() function takes data databse.

if (tblcategories == null)      {       tblcategories = new datatable();       tblcategories=objdac.loadcategoryindropdownlist();       // inserts new row in filled datatable.       //this new row contains static data user        //instruction text such as" select item"       datarow dr=tblcategories.newrow();       dr["categoryid"]=0;       dr["categoryname"]="--select item--";       tblcategories.rows.insertat(dr,0);       //cache datatable in cache memory duration of 1 hour...       cache.insert("categories", tblcategories, null,               datetime.now.addhours(1), cache.noslidingexpiration);     } 

then bind dropdown datatable

dropdownlist1.datasource = tblcategories  dropdownlist1.datatextfield ="a descriptive field table";  dropdownlist1.datavaluefield="a key / value field table";  dropdownlist1.databind(); 

you can refer here http://www.codeproject.com/articles/10033/a-generic-loading-of-data-in-a-dropdownlist-using