JQuery Validate - DropDown - jquery-validate

Question

I'm using the JQuery Validate plugin to validate my form. I'm able to validate text boxes but not DropDown. Can someone let me know how to validate dropdown?
<asp:FormView ID="fv_LeaveRequest" runat="server" DataKeyNames="REQ_ACTION_ID">
<InsertItemTemplate>
<label>Leave Type</label>
<asp:DropDownList ID="ddl_LeaveType" runat="server">
</asp:DropDownList>
<label>Leave Date</label>
<asp:TextBox ID="tb_leaveDate" runat="server" CssClass="date"></asp:TextBox>
<asp:Button ID="LeaveReqBtn" runat="server" Text="Submit Leave Request" CommandName="CustomInsert"
CssClass="button-position" />
</InsertItemTemplate>
<ItemTemplate>
<asp:LinkButton ID="Edit" runat="server" Text="Edit / Change Request" CommandName="Edit" CssClass="button-position btn-padding" />
<label>Leave Type</label>
<asp:DropDownList ID="ddl_LeaveType" runat="server">
</asp:DropDownList>
<label>Leave Date</label>
<asp:TextBox ID="tb_leaveDate" runat="server" CssClass="date"></asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:LinkButton ID="Cancel" Text="Cancel" CommandName="Cancel" runat="server" CssClass="button-position btn-padding" />
<label>Leave Type</label>
<asp:DropDownList ID="ddl_LeaveType" runat="server">
</asp:DropDownList>
<label>Leave Date</label>
<asp:TextBox ID="tb_leaveDate" runat="server" CssClass="date"></asp:TextBox>
</EditItemTemplate>
$("#form1").validate({
rules: {
LeaveType: "required",
LeaveDate: "required"
},
messages: {
LeaveType: "Select a value from DropDown",
LeaveDate: "This field is required"
}
});