using MSXML2;

下面就是主要的代码：

private void Page_Load(object sender, System.EventArgs e)
{ 
 string Url = http://dotnet.aspx.cc/Images/logoSite.gif;
 string StringFileName = Url.Substring(Url.LastIndexOf(/) + 1);
 string StringFilePath = Request.PhysicalApplicationPath;
 if(!StringFilePath.EndsWith(/)) StringFilePath += /;
 MSXML2.XMLHTTP _xmlhttp = new MSXML2.XMLHTTPClass();
 _xmlhttp.open(GET,Url,false,null,null);
 _xmlhttp.send();
 if( _xmlhttp.readyState == 4 )
 {
  if(System.IO.File.Exists(StringFilePath + StringFileName))
   System.IO.File.Delete(StringFilePath + StringFileName);
  System.IO.FileStream fs = new System.IO.FileStream(StringFilePath + StringFileName, System.IO.FileMode.CreateNew);
  System.IO.BinaryWriter w = new System.IO.BinaryWriter(fs);
  w.Write((byte[])_xmlhttp.responseBody);
  w.Close();
  fs.Close();
  Response.Write (文件已经得到。<br><a href=' + Request.ApplicationPath + StringFileName +' target='_blank'>);
  Response.Write (查看 + StringFileName + </a>);
 }
 else
 Response.Write (_xmlhttp.statusText);
 Response.End();
}