asp.net - .DataSource outputs a duplicate list? -

asp.net - .DataSource outputs a duplicate list? -

when user selects value drop downwards list , clicks on button, value added sec list (which displayed on screen).

the problem beingness when user clicks on button, selected value added sec list drop downwards list duplicated , added original drop downwards list.

so have 1, 2, 3 in original drop down, user selects '1' , presses button. '1' added sec list , displayed on screen when user clicks on drop downwards contains 2, 3, 1, 2, 3

iv went through code break point , think has .datasource.

protected void updatepage() { int id = system.convert.toint32(id.value); list<contractor> allcontractors = new list<contractor>(); clarkedbdatacontext db = new clarkedbdatacontext(); allsubcontractors = (from boqcontractors in db.boq_contractors boqcontractors.bill_of_quantity_id == tempboqid select boqcontractors.contractor).tolist(); repeatershowcontractorname.datasource = allcontractors; repeatershowcontractorname.databind(); ienumerable<sub> availablecontractors = (from sc in db.contractors select sc).tolist().except(allcontractors); //i've tried set null test it, no avail dropdownlistcontractors.datasource = null; dropdownlistcontractors.datasource = availablecontractors; dropdownlistcontractors.databind(); }

the original values exist in ddl because of viewstate , postback. ddl repopulated on postback. why original values there.

i not sure why need reget info db in utilize case. if need refresh list db, phone call dropdownlistcontractors.clear() before setting datasource. clear out list.

but, stated earlier, don't think need rebind ddl db. remove these lines code (when posting back) , should work want it:

ienumerable<sub> availablecontractors = (from sc in db.contractors select sc).tolist().except(allcontractors); //i've tried set null test it, no avail dropdownlistcontractors.datasource = null; dropdownlistcontractors.datasource = availablecontractors; dropdownlistcontractors.databind();

asp.net datasource