由当前日期得到本周的开始和结束日期

/// <summary>
  /// 本周起止时间
  /// </summary>
  /// <param name="dt"></param>
  /// <returns></returns>
  private string weekrange(System.DateTime dt) 
  { 
   int weeknow = Convert.ToInt32(dt.DayOfWeek); 
   int daydiff = (-1) * weeknow; 
   int dayadd = 6-weeknow; 
   string datebegin = System.DateTime.Now.AddDays(daydiff).ToString("yyyyMMdd"); 
   string dateend = System.DateTime.Now.AddDays(dayadd).ToString("yyyyMMdd"); 
   return datebegin + " - " +dateend; 
  } 

  /// <summary>
  /// 返回指定URL的源代码
  /// </summary>
  /// <param name="url"></param>
  private string GetHTML( string url,string tag)
  {
   byte[] buf = new byte[38192]; 
   System.Net.WebRequest request =  WebRequest.Create(url);;
   WebResponse response =request.GetResponse(); 
   Stream resStream = response.GetResponseStream(); 
   int count = resStream.Read(buf, 0, buf.Length); 
   string result = Encoding.Default.GetString(buf, 0, count); 
   resStream.Close(); 
   Regex   reg=new   Regex(@"(?<"+tag+">.*?</"+tag+">)",RegexOptions.IgnoreCase);   
   string   output=reg.Match(result).Value;
   return StripHTML(output);
  }
  /// <summary>
  /// 去除HTML标记
  /// </summary>
  /// <param name="strHtml">包括HTML的源码 </param>
  /// <returns>已经去除后的文字</returns>
  public static string StripHTML(string strHtml)
  {
   string [] aryReg ={
          @"<script[^>]*?>.*?</script>",

          @"<(\/\s*)?!?((\w+:)?\w+)(\w+(\s*=?\s*(([""'])(file://[""'tbnr]|[^/7])*?/7|/w+)|.{0})|/s)*?(///s*)?>",
          @"([\r\n])[\s]+",
          @"&(quot|#34);",
          @"&(amp|#38);",
          @"&(lt|#60);",
          @"&(gt|#62);", 
          @"&(nbsp|#160);", 
          @"&(iexcl|#161);",
          @"&(cent|#162);",
          @"&(pound|#163);",
          @"&(copy|#169);",
          @"&#(\d+);",
          @"-->",
          @"<!--.*\n"
         
         };

   string [] aryRep = {
           "",
           "",
           "",
           "\"",
           "&",
           "<",
           ">",
           " ",
           "\xa1",//chr(161),
           "\xa2",//chr(162),
           "\xa3",//chr(163),
           "\xa9",//chr(169),
           "",
           "\r\n",
           ""
          };

   string newReg =aryReg[0];
   string strOutput=strHtml;
   for(int i = 0;i<aryReg.Length;i++)
   {
    Regex regex = new Regex(aryReg[i],RegexOptions.IgnoreCase );
    strOutput = regex.Replace(strOutput,aryRep[i]);
   }

   strOutput.Replace("<","");
   strOutput.Replace(">","");
   strOutput.Replace("\r\n","");


   return strOutput;
  }