Sub report issue in rdlc

I have developed RDLC report and a drill through, it works but problem is that when drill through report appears , it stays out of layout, like below footer, why ? And when i go back to main report then it also become out of layout why ?

public partial class Report_GetComplaints_SdpoReplies : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // Two Lines Below Helps in Triggering Generate Report Button Upon Pressing ENTER Button.

        this.Page.Form.DefaultButton = btnPreview.UniqueID;
        this.Page.Form.DefaultFocus = btnPreview.ClientID;

        if (Session.Count <= 0)
        {
            //Checks if User Has Not Logged In then Must Be Redirected To Login Page.

            Response.Redirect("login.aspx");
        }

        if (!IsPostBack)
        {
            //Checks if Page is Called For the First Time or Because of Postback By User e.g. Clicking 'Submit' Button

            ReportViewer1.AsyncRendering = false;
            ReportViewer1.SizeToReportContent = true;
            ReportViewer1.ZoomMode = ZoomMode.FullPage;
            this.ReportViewer1.Reset();

        }
    }
    protected void btnGenReport_Click(object sender, EventArgs e)
    {
        //This Event Generates Report of Complaints Between Specific Dates.

        try
        {
            DataSet dss = (DataSet)Session["UserData"];
            int UserID = Convert.ToInt32(dss.Tables[0].Rows[0][3].ToString());
            int DesigID = Convert.ToInt32(dss.Tables[0].Rows[0][4].ToString());

            MyComplaints obj = new MyComplaints();
            ReportViewer1.ProcessingMode = ProcessingMode.Local;
            ReportViewer1.LocalReport.ReportPath = Server.MapPath("~/Reports/Report_GetComplaints_ForSdpoReplies.rdlc");
            DataTable dt = ManageRecievedMessage.Report_SearchSmsRepliesAgainstComplaintsByComplaintCode(txtComplaintCode.Text);

            if (dt.Rows.Count <= 0)
            {
                HiddenFieldSetMessage.Value = "WrongDatesComb";
                HiddenFieldShowMessage.Value = "True";
                ReportViewer1.Visible = false;
            }
            else
            {
                ReportDataSource rpds = new ReportDataSource("DataSet1", dt);
                ReportViewer1.LocalReport.DataSources.Clear();
                ReportViewer1.LocalReport.DataSources.Add(rpds);
                ReportViewer1.Visible = true;
            }

        }
        catch (Exception ex)
        {
            Response.Write(ex.Message.ToString());
        }
    }
    protected void ReportViewer1_Drillthrough(object sender, DrillthroughEventArgs e)
    {


        try
        {
            LocalReport Report = (LocalReport)e.Report;
            Report.DataSources.Add(new ReportDataSource("DataSet1", LoadValues(e.Report.GetParameters())));
            Report.Refresh();
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }

    }

    private DataTable LoadValues(ReportParameterInfoCollection c)
    {
        try
        {
            DataSet1TableAdapters.SubReport_RepliesAgainstComplaints_SpTableAdapter adp = new
             DataSet1TableAdapters.SubReport_RepliesAgainstComplaints_SpTableAdapter();

            return adp.GetData(Convert.ToString(c["ComplaintCode"].Values[0]));

        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
            throw;
        }
    }
}

public partial class Report_GetComplaints_SdpoReplies : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // Two Lines Below Helps in Triggering Generate Report Button Upon Pressing ENTER Button.

        this.Page.Form.DefaultButton = btnPreview.UniqueID;
        this.Page.Form.DefaultFocus = btnPreview.ClientID;

        if (Session.Count <= 0)
        {
            //Checks if User Has Not Logged In then Must Be Redirected To Login Page.

            Response.Redirect("login.aspx");
        }

        if (!IsPostBack)
        {
            //Checks if Page is Called For the First Time or Because of Postback By User e.g. Clicking 'Submit' Button

            ReportViewer1.AsyncRendering = false;
            ReportViewer1.SizeToReportContent = true;
            ReportViewer1.ZoomMode = ZoomMode.FullPage;
            this.ReportViewer1.Reset();

        }
    }
    protected void btnGenReport_Click(object sender, EventArgs e)
    {
        //This Event Generates Report of Complaints Between Specific Dates.

        try
        {
            DataSet dss = (DataSet)Session["UserData"];
            int UserID = Convert.ToInt32(dss.Tables[0].Rows[0][3].ToString());
            int DesigID = Convert.ToInt32(dss.Tables[0].Rows[0][4].ToString());

            MyComplaints obj = new MyComplaints();
            ReportViewer1.ProcessingMode = ProcessingMode.Local;
            ReportViewer1.LocalReport.ReportPath = Server.MapPath("~/Reports/Report_GetComplaints_ForSdpoReplies.rdlc");
            DataTable dt = ManageRecievedMessage.Report_SearchSmsRepliesAgainstComplaintsByComplaintCode(txtComplaintCode.Text);

            if (dt.Rows.Count <= 0)
            {
                HiddenFieldSetMessage.Value = "WrongDatesComb";
                HiddenFieldShowMessage.Value = "True";
                ReportViewer1.Visible = false;
            }
            else
            {
                ReportDataSource rpds = new ReportDataSource("DataSet1", dt);
                ReportViewer1.LocalReport.DataSources.Clear();
                ReportViewer1.LocalReport.DataSources.Add(rpds);
                ReportViewer1.Visible = true;
            }

        }
        catch (Exception ex)
        {
            Response.Write(ex.Message.ToString());
        }
    }
    protected void ReportViewer1_Drillthrough(object sender, DrillthroughEventArgs e)
    {


        try
        {
            LocalReport Report = (LocalReport)e.Report;
            Report.DataSources.Add(new ReportDataSource("DataSet1", LoadValues(e.Report.GetParameters())));
            Report.Refresh();
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }

    }

    private DataTable LoadValues(ReportParameterInfoCollection c)
    {
        try
        {
            DataSet1TableAdapters.SubReport_RepliesAgainstComplaints_SpTableAdapter adp = new
             DataSet1TableAdapters.SubReport_RepliesAgainstComplaints_SpTableAdapter();

            return adp.GetData(Convert.ToString(c["ComplaintCode"].Values[0]));

        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
            throw;
        }
    }
}