Как правильно делать валидацию на jQuery на календаре текстовых полях

<pre>$(document).ready(function () {
            $("#txtFromDate.ClientID").focusin(function () {
               
            });
        var obj = {};
        obj.date3 = $.trim($("[id*=txtFromDate]").val());
        obj.date4 = $.trim($("[id*=txtToDate]").val());
        if (obj.date3 != "" && obj.date4 != "") {

            $.ajax({
                type: "POST",
                url: 'LMSEmployee.aspx/GetCurrentTime',
                data: JSON.stringify(obj),
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (message) {
                    if (message == "") {
                        alert("Not allowed to take leave");
                    }
                    else {
                        alert("");
                    }
                }
            });
        }
            else
            return false;
       
        });

<pre><asp:TextBox ID="txtFromDate" runat="Server" placeholder="Select From Date" CssClass="lmsFieldValue"

                        OnTextChanged="txtFromDate_TextChanged"></asp:TextBox>
                    <asp:CalendarExtender ID="CalendarExtender1" CssClass="calendercssclass" runat="server"

                        TargetControlID="txtFromDate" Format="MM/dd/yyyy" OnClientDateSelectionChanged="ValidateDate">
                    </asp:CalendarExtender>


<asp:TextBox ID="txtToDate" runat="Server" placeholder="Select To Date" CssClass="lmsFieldValue"></asp:TextBox>
                    <asp:CalendarExtender ID="CalendarExtender2" CssClass="calendercssclass" runat="server"

                        TargetControlID="txtToDate" Format="MM/dd/yyyy" OnClientDateSelectionChanged="ValidateDate">
                    </asp:CalendarExtender>