protected void bExport_Click(object sender, EventArgs e)
    {
 DataTable resultToExcel = Export.ExportToExcel(DateTime.Parse(txtFrom.Text), DateTime.Parse(txtTo.Text));
HtmlTable results = Export.ConvertToHtml(resultToExcel);  //----------********
                Response.Clear();
                Response.Cache.SetCacheability(HttpCacheability.NoCache);
                Response.AddHeader("Content-Disposition", "attachment; filename=Test.xls");
                Response.ContentType = "application/vnd.ms-excel";
                //Response.Charset = "win-1251";   закоментировал так как это не помогло
                //Response.ContentEncoding = Encoding.GetEncoding("win-1251");
                //Response.HeaderEncoding = Encoding.GetEncoding("win-1251");
                StringWriter stringWrite = new StringWriter();
                HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
                results.RenderControl(htmlWrite);
                Response.Write(stringWrite.ToString());
                resultToExcel.Dispose();
                results.Dispose();
                Response.End();
}
//---------------------------------------------------------------------*******

public static HtmlTable ConvertToHtml(DataTable dataTable)
    {
        var htmlTable = new HtmlTable();
        if (dataTable == null) return htmlTable;
        HtmlTableRow htmlRow = new HtmlTableRow();
        htmlTable.Rows.Add(htmlRow);
        foreach (DataColumn column in dataTable.Columns)
        {
            HtmlTableCell Cell = new HtmlTableCell();
            Cell.InnerText = column.ColumnName;
            Cell.BgColor = "Gray";
            Cell.Align = "Center";
            Cell.Attributes.Add("style", "font-size:14px; color: white;");
            htmlRow.Cells.Add(Cell);
        }
        foreach (DataRow row in dataTable.Rows)
        {
            htmlRow = new HtmlTableRow();
            htmlTable.Rows.Add(htmlRow);
            foreach (DataColumn column in dataTable.Columns)
            {
                HtmlTableCell Cell = new HtmlTableCell();
                Cell.InnerText = row[column].ToString();
                htmlRow.Cells.Add(Cell);
            }
        }
        return htmlTable;
    }

Dim strMeta As String = "<meta http-equiv=" & Chr(39) & "Content-Type" & Chr(39) & " content=" & Chr(39) & "text/html; charset=utf-8" & Chr(39) & ">"
Response.Write(strMeta & stringWrite.ToString())