dropdownlist 控制显示与不显示的方法

function DropDownListJob_Change()
{
   var DropDownListJobValue=document.getElementById("ctl00_ContentPlaceHolder1_DropDownListJob").value;
  
   var DropDownListWhere=document.getElementById("ctl00_ContentPlaceHolder1_DropDownListWhere");
  
   var TextBoxBFDes=document.getElementById("ctl00_ContentPlaceHolder1_TextBoxBFDes");
   if(DropDownListJobValue=="4")
      {
         DropDownListWhere.style.display="block";
      }
   else
     {
        DropDownListWhere.style.display="none";
     } 
  
  
}