文件下载的一个类[原创]

/// <summary>
 /// 下载文件
 /// </summary>
 public class BDDownLoadFile
 {
  private string Url;     //要下载的文件URL地址
  private string SavePath;   //要保存的文件的目录  
  private string errMsg;    //保存错误信息
  private string RegValue = @"http://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?"; 
  private string SaveFile;   //生成的文件

  public BDDownLoadFile(string url,string path)
  {
   Url = url;
   SavePath = path;
   this.SaveFile = GetFileName();
  }

  /// <summary>
  /// 返回错误信息
  /// </summary>
  public string ErrorMessage
  {
   get
   {
    return this.errMsg;
   }
  }

  public string GetSaveFile
  {
   get
   {
    return this.SaveFile;
   }
  }
  public bool DownLoadFile()
  {
   bool result = true;
   if( !CheckUrl(this.Url) )
   {
    this.errMsg = "网址不合法！";
    return false;
   }
   WebClient objWC = new WebClient();
   objWC.Credentials = CredentialCache.DefaultCredentials;
   try
   {       
    byte[] tmpData = objWC.DownloadData(this.Url);
    if(tmpData.Length > 0)
    {
     FileStream objFS = new FileStream(this.SaveFile,FileMode.Create);
     objFS.Write(tmpData,0,(int)tmpData.Length); //向文件写入数据
     objFS.Close();
     this.errMsg = "有数据！";
    }
    else
    {
     result = false;
     this.errMsg = "没有接收到任何数据！";
    }
   }
   catch(System.Net.WebException e)
   {
    this.errMsg += "<li>下载数据时发生错误！" + e.Message;
    return false;
   }
   catch(System.UriFormatException e)
   {
    this.errMsg += "<li>访问的网址无效！" + e.Message;
    return false;
   }
   catch(Exception e)
   {
    this.errMsg = "错误信息:<li>."+e.Message;
    result = false;
   }
   finally
   {
    objWC.Dispose();
   }
   return result;
  }

  /// <summary>
  /// 检查网址是否合法
  /// </summary>
  /// <param name="chkUrl">要检查的网址</param>
  /// <returns></returns>
  private bool CheckUrl(string chkUrl)
  {
   Regex reg = new Regex(RegValue);
   Match match = reg.Match(chkUrl);
   return match.Success;
  }

  /// <summary>
  /// 取得网址是否有文件，如果有文件，则处理，若没有，则返回.html
  /// </summary>
  /// <param name="chkUrl"></param>
  /// <returns></returns>
  private string GetFileType(string chkUrl)
  {
   if(chkUrl.LastIndexOf("/") == (chkUrl.Length-1)) //没有具体文件
    return "html";
   int j = 0;
   for(int i = 0; i < chkUrl.Length; i++)
   {
    if(chkUrl.IndexOf("/",i)>-1)
    {
     i = chkUrl.IndexOf("/",i);
     j++;
    }
   }
   if( j < 3)
    return "html";
   //取得"/"后的字符，然后得出文件类型   
   string end = chkUrl.Substring(chkUrl.LastIndexOf(".")+1);
   switch(end)
   {
    case "asp":
    case "aspx":
    case "jsp":
    case "php":
     return "html";
    default:
     return end;    
   }
  }

  private string GetFileName()
  {
   string fileName = this.SavePath + "\\" + System.DateTime.Now.Year.ToString()+System.DateTime.Now.Month.ToString()+System.DateTime.Now.Day.ToString()+System.DateTime.Now.Minute.ToString()+System.DateTime.Now.Second.ToString()+Common.MakeRandom(4).ToString()+"."+GetFileType(this.Url);
   for(;File.Exists(fileName);) 
   {
    fileName = this.SavePath + "\\" + System.DateTime.Now.Year.ToString()+System.DateTime.Now.Month.ToString()+System.DateTime.Now.Day.ToString()+System.DateTime.Now.Minute.ToString()+System.DateTime.Now.Second.ToString()+Common.MakeRandom(4).ToString()+"\\"+GetFileType(this.Url);
   }
   return fileName;
  }
 } //BDDownLoadFile end

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