c# - Columns in DataTable Disappearing -

i have datatable has columns generated upon page load. not wish table re-created every time postback occurs, have in no-postback if statement. wit:

datatable purchase_display_data = new datatable();  protected void page_load(object sender, eventargs e) {     if(!ispostback)     {         datacolumn rownumber = new datacolumn();         rownumber.datatype = system.type.gettype("system.int16");         rownumber.autoincrement = true;         rownumber.autoincrementseed = 1;         rownumber.autoincrementstep = 1;          purchase_display_data.columns.add(rownumber);         purchase_display_data.columns.add("item");         purchase_display_data.columns.add("charge");     } } 

later, i'm attempting add data after pressing button. with:

protected void buttonok_click(object sender, eventargs e) {     datarow newline = purchase_display_data.newrow();     newline[1] = "1";     newline[2] = "2";     purchase_display_data.rows.add(newline); } 

upon pressing said button, return error stating column wasn't found. in debug, notice datatable has 0 columns, despite having created them upon page load (per debug , other testing). columns seem have vanished. can tell me why occurring and, of course, how fix it.

you lose data on postbacks. that's normal. have use of state management mechanisms viewstate or session mention few.

you can try using viewstate:

private datatable purchase_display_data {         {         if (viewstate["purchase_display_data"] == null)             viewstate["purchase_display_data"] = new datatable();         return (datatable)viewstate["purchase_display_data"];     }     set { viewstate["purchase_display_data"] = value; } }