vb.net - Change Textbox value after selection from Dropdownlist -

when select value first dropdownlist, populates second dropdownlist , textbox correct values. however, when select different value second dropdown, textbox value still retains same value populated with. please point out doing wrong?

 if ds.tables(0).rows(0).item(3).tostring = "m"             dropdownlist2.items.insert(0, "member")             dropdownlist2.items.insert(1, "non-member")             dropdownlist2.items.insert(2, "")             textbox1.text = "m"         elseif ds.tables(0).rows(0).item(3).tostring = "nm"             dropdownlist2.items.insert(0, "non-member")             dropdownlist2.items.insert(1, "member")             dropdownlist2.items.insert(2, "")             textbox1.text = "nm"         else             dropdownlist2.items.insert(0, "")             dropdownlist2.items.insert(1, "member")             dropdownlist2.items.insert(2, "non-member")             textbox1.text = ""         end if            if dropdownlist2.selectedvalue = "member"             textbox1.text = ""             textbox1.text = "m"         elseif dropdownlist2.selectedvalue = "non-member"             textbox1.text = ""             textbox1.text = "nm"         else             textbox1.text = ""  end if