I was creating another usercontrol with Telerik's RadGrid and Calendar.

<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>
<table class="style1">
    <tr>
        <td>From</td>
        <td>To</td>
    </tr>
    <tr>
        <td><asp:Calendar ID="Calendar1" runat="server" SelectionMode="Day"></asp:Calendar></td>
        <td><asp:Calendar ID="Calendar2" runat="server" SelectionMode="Day"></asp:Calendar></td>
    </tr>
    <tr>
        <td><asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" /></td>
        <td><asp:Button ID="btnClear" runat="server" Text="Clear" OnClick="btnClear_Click" /></td>
    </tr>
</table>
<telerik:RadGrid ID="RadGrid1" runat="server">
    <MasterTableView CommandItemDisplay="Top"></MasterTableView>
</telerik:RadGrid>

and I am using Linq in code-behind:

    Entities1 entities = new Entities1();

    public static object DataSource = null;

    protected void Page_Load(object sender, EventArgs e) {
        if (DataSource == null) {
            DataSource = (from entity in entities.nsc_moneytransaction
                          select new {
                              date = entity.transaction_date.Value,
                              username = entity.username,
                              cashbalance = entity.cash_balance
                          }).OrderByDescending(a => a.date);
        }
        BindData();
    }

    public void BindData() {
        RadGrid1.DataSource = DataSource;
    }

    protected void btnSubmit_Click(object sender, EventArgs e) {
        DateTime startdate = new DateTime();
        DateTime enddatedate = new DateTime();
        if (Calendar1.SelectedDate != null && Calendar2.SelectedDate != null) {
            startdate = Calendar1.SelectedDate;
            enddatedate = Calendar2.SelectedDate;
            var queryDateRange = from entity in entities.nsc_moneytransaction
                                 where DateTime.Parse(entity.transaction_date.Value.ToShortDateString())
                                        >= DateTime.Parse(startdate.ToShortDateString())
                                    && DateTime.Parse(entity.transaction_date.Value.ToShortDateString()) 
                                        <= DateTime.Parse(enddatedate.ToShortDateString())
                                 select new {
                                     date = entity.transaction_date.Value,
                                     username = entity.username,
                                     cashbalance = entity.cash_balance
                                 };
            DataSource = queryDateRange.OrderByDescending(a => a.date);
        } else if (Calendar1.SelectedDate != null) {
            startdate = Calendar1.SelectedDate;
            var querySetDate = from entity in entities.nsc_moneytransaction
                               where entity.transaction_date.Value == startdate
                               select new {
                                   date = entity.transaction_date.Value,
                                   username = entity.username,
                                   cashbalance = entity.cash_balance
                               };
            DataSource = querySetDate.OrderByDescending(a => a.date); ;
        }
        BindData();
    }

    protected void btnClear_Click(object sender, EventArgs e) {
        Calendar1.SelectedDates.Clear();
        Calendar2.SelectedDates.Clear();
    }

The problems are, (1) when I click the submit button. the data in the RadGrid is not changed. (2) how can we check if there is nothing selected in the Calendar controls, because there is a date (01/01/0001) set even if we do not select anything from that calendar, thus Calendar1.SelectedDate != null is not enough. =(

Thanks.