Untitled

public partial class MainForm : System.Web.UI.Page
{

    private ServData.DataServiceClient OpenSession()
    {
        var clnt = new ServData.DataServiceClient();
        clnt.ClientCredentials.Windows.ClientCredential.UserName = @"******";
        clnt.ClientCredentials.Windows.ClientCredential.Password = "*******";
        clnt.SetCurrentUser(new Guid("*******"));
        return clnt;
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        if (cbxReports.Items.Count > 0) return;
        using (var clnt = OpenSession())
        {
            clnt.GetReportList().ToList().ForEach(c => cbxReports.Items.Add(c));
        }
    }

    protected void cbxReports_SelectedIndexChanged(object sender, EventArgs e)
    {
        WebReport1.Refresh();
    }

    protected void WebReport1_StartReport(object sender, EventArgs e)
    {
        if (string.IsNullOrWhiteSpace(cbxReports.SelectedValue)) return;

        var rep = sender as FastReport.Web.WebReport;
        using (var clnt = OpenSession())
        {
            var data = clnt.GetReport(cbxReports.SelectedValue, DateTime.Today.AddDays(-100), DateTime.Today);
            using (var ms = new MemoryStream(data))
            {
                rep.Report.LoadPrepared(ms);
            }
        }
        rep.ReportDone = true;
    }

}

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="MainForm.aspx.cs" Inherits="LabDeparts.RepClientWeb.MainForm" %>

    <%@ Register assembly="FastReport.Web, Version=1.6.28.0, Culture=neutral, PublicKeyToken=db7e5ce63278458c" namespace="FastReport.Web" tagprefix="cc1" %>

    <!DOCTYPE html>

    <html xmlns="http://www.w3.org/1999/xhtml">
    <head runat="server">
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
        <title></title>
    </head>
    <body>
        <form id="form1" runat="server">
            <asp:Panel ID="Panel1" runat="server">
                <asp:Label ID="Label1" runat="server" Text="Label">Отчет: </asp:Label>
                <asp:DropDownList ID="cbxReports" runat="server" Width="40%" OnSelectedIndexChanged="cbxReports_SelectedIndexChanged" AutoPostBack="True"></asp:DropDownList>
            </asp:Panel>
            <br />
            <cc1:WebReport ID="WebReport1" runat="server" Width="100%" OnStartReport="WebReport1_StartReport" />
        </form>
    </body>
    </html>

var data = clnt.GetReport(cbxReports.SelectedValue, DateTime.Today.AddDays(-100), DateTime.Today);