Reset Dropdown list in sharepoint webpart

Hello Techies,
I have a webpartwhere there are fields like:

• Year(DropDown)
• Month(DropDown)
• Employer(txtbox)
• CTClakhs(txtbox)
• CTCthousand(txtbox)
• Currency(Dropdown)

Here i got the requirement like if Year and Month values are "0" then I need to disable and reset the values of other fields say Employer,CTClakhs,CTCThousandsand Currency
so for this I wrote the validations in javascript which are called onChange event of Year and Month dropdowns

 function clearFunction() {

        if (document.getElementById('ctl00_PlaceHolderMain_form1_ddlYears').value == 0 && document.getElementById('ctl00_PlaceHolderMain_form1_ddlMonth').value == 0) {
            document.getElementById('ctl00_PlaceHolderMain_form1_txtEmployer').value = "";
            document.getElementById('ctl00_PlaceHolderMain_form1_txtLacs').value = "";
            document.getElementById('ctl00_PlaceHolderMain_form1_txtThousand').value = "";
            document.getElementById("ctl00_PlaceHolderMain_form1_ddlCurrency").selectedIndex = 0;
            //document.getElementById("ctl00_PlaceHolderMain_form1_ddlCurrency").value = 0;
            document.getElementById('ctl00_PlaceHolderMain_form1_txtEmployer').disabled = true;
            document.getElementById('ctl00_PlaceHolderMain_form1_txtLacs').disabled = true;
            document.getElementById('ctl00_PlaceHolderMain_form1_txtThousand').disabled = true;
            document.getElementById("ctl00_PlaceHolderMain_form1_ddlCurrency").disabled = true;

        }
        else {

                            document.getElementById('ctl00_PlaceHolderMain_form1_txtEmployer').disabled = false;
                            document.getElementById('ctl00_PlaceHolderMain_form1_txtLacs').disabled = false;
                            document.getElementById('ctl00_PlaceHolderMain_form1_txtThousand').disabled = false;
                            document.getElementById('ctl00_PlaceHolderMain_form1_ddlCurrency').disabled = false;

        }

But here values of all the fields are getting reset except Currency dropdown 
Later I check the value of Currency through console and the value was getting reset but it was not reflected in UI (still shows selected value)

Here I wanted to reset the value of Currency dropdown :( :( 

Again for this i tried to achieve .cs file and made the change on .ascx file like

<asp:UpdatePanel ID="OuterUpdatePanel" runat="server"  UpdateMode="Conditional"><ContentTemplate><tr class="contactForm twoSelects"><td><label for="exp">
                Total Experience <span class="required"></span></label></td><td class="selector" id="uniform-undefined"><div><asp:DropDownList ID="ddlYears" CssClass="uniformselect" onSelectedindexChanged="drp_Commoncleardata" autopostback="true"  runat="server" Width="100%"
                    BackColor="Transparent"></asp:DropDownList></div><div><asp:DropDownList ID="ddlMonth"  CssClass="uniformselect" onselectedindexchanged="drp_Commoncleardata" autopostback="true"  runat="server" Width="100%"
                    BorderStyle="None"><asp:ListItem Value="-1">-- In Months -- </asp:ListItem><asp:ListItem Value="0">0 </asp:ListItem><asp:ListItem Value="1">1</asp:ListItem><asp:ListItem Value="2">2</asp:ListItem><asp:ListItem Value="3">3</asp:ListItem><asp:ListItem Value="4">4</asp:ListItem><asp:ListItem Value="5">5</asp:ListItem><asp:ListItem Value="6">6</asp:ListItem><asp:ListItem Value="7">7</asp:ListItem><asp:ListItem Value="8">8</asp:ListItem><asp:ListItem Value="9">9</asp:ListItem><asp:ListItem Value="10">10</asp:ListItem><asp:ListItem Value="11">11</asp:ListItem></asp:DropDownList></div></td></tr><tr class="contactForm"><td><label for="org">
                Current Organization <!--<span class="required"></span>--></label></td><td><asp:TextBox ID="txtEmployer" runat="server" CssClass="textbox" MaxLength="50" BackColor="Transparent"></asp:TextBox></td></tr><tr class="contactForm"><td></td><td colspan="2"><label style="width: 250px !important;"><!--(Enter NA in case of fresher)--></label></td></tr><tr class="contactForm"><td><label for="CTC">
                Current Compensation (CTC) <!--<span class="required"></span>--></label></td><td><asp:TextBox ID="txtLacs" onkeypress="return numbersonly(event, false)" runat="server"
                CssClass="textbox_CTC" MaxLength="10" BackColor="Transparent"></asp:TextBox>&nbsp;&nbsp;&nbsp;<span
                    class="field_Desc">Lacs</span> &nbsp;&nbsp;<asp:TextBox ID="txtThousand" onkeypress="return numbersonly(event, false)" runat="server"
                CssClass="textbox_CTC" MaxLength="10"></asp:TextBox><br />&nbsp;&nbsp;&nbsp;<span class="field_Desc">Thousand</span></td></tr><tr class="contactForm"><td><label for="currency">
                Currency</label></td><td><asp:DropDownList ID="ddlCurrency" runat="server"  CssClass="combobox_new uniformselect"  Width="100%"  BackColor="Transparent" ></asp:DropDownList></td></tr></ContentTemplate><Triggers><asp:AsyncPostBackTrigger ControlID="ddlYears" EventName="SelectedIndexChanged" /><asp:AsyncPostBackTrigger ControlID="ddlMonth" EventName="SelectedIndexChanged" /></Triggers></asp:UpdatePanel>

.cs code 

protected void drp_Commoncleardata(object sender, EventArgs e)
        {
            if ((ddlMonth.SelectedValue == "0") && (ddlYears.SelectedValue == "0"))
            {
                ddlCurrency.ClearSelection();
            }

        }

the above code is also not helping me 
Please help and let me know what needs to be done to reset DropDown selection