获取DropDownList选择项的值

<script type="text/javascript" language="javascript"> 
          function CheckDropDownList() { 
              var dropDownList = document.getElementById("<%=DropDownListID.ClientID %>"); //获取DropDownList控件 
              var dropDownListValue = dropDownList.options[dropDownList.selectedIndex].value; //获取选择项的值 
              //注：DropDownListID是DropDownList控件的ID。 
   
              //JS验证是否有非0值： 
              if (dropDownListValue == 0) { 
                  alert("请选择……."); 
                 dropDownList.focus(); 
                 return false; 
             } 
             else { 
                 return true; 
             } 
         } 
     </script>

function enble() {
            var ddl = document.getElementById("<%=ddl_YesNo_State.ClientID %>");
            var txt = document.getElementById("<%=btn_SaveALL.ClientID %>");
            var ddlValue = ddl.options[ddl.selectedIndex].value;
            if (ddlValue.toString() == "已发放") {
                txt.disabled = true;
            }
            else {
                txt.disabled = false;
            }
        }