用C#写一个下载程序

try    
{    
if(!Page.IsPostBack)    
{    
string   strFileName="";    
strFileName=Request.QueryString["FILE_NAME"].ToString();    
strFileName=HttpUtility.UrlEncode(System.Text.Encoding.UTF8.GetBytes(strFileName));    
Response.Clear();    
Response.ContentType="application/x-msexcel";    
Response.AddHeader("Content-Disposition", "inline; filename="+strFileName);    
System.IO.FileStream MyFileStream=new FileStream(Request.QueryString["REPORT_FILE"].ToStrin(),System.IO.FileMode.Open,System.IO.FileAccess.Read,System.IO.FileShare.Read);    
long   FileSize=MyFileStream.Length;    
byte[] Buffer=new byte[(int)FileSize];    
MyFileStream.Read(Buffer,   0,   (int)FileSize);    
MyFileStream.Close();    
Response.BinaryWrite(Buffer);    
}    
}    
catch(Exception exp)    
{    
Response.Write("导出数据错误!");    
}