文件（图片生产缩略图）的上传与下载

// 得到用户要上传的文件名
             string  strFilePathName  =  loFile.PostedFile.FileName;
             string  strFileName  =  Path.GetFileName(strFilePathName);
             int  FileLength  =  loFile.PostedFile.ContentLength;
             if (FileLength <= 0 )
                 return ;
             try
             {//上传文件
                Byte[] FileByteArray = new Byte[FileLength]; //图象文件临时储存Byte数组
                Stream StreamObject = loFile.PostedFile.InputStream; //建立数据流对像
                //读取图象文件数据，FileByteArray为数据储存体，0为数据指针位置、FileLnegth为数据长度
                StreamObject.Read(FileByteArray,0,FileLength); 
                //建立SQL Server链接
                string strCon = System.Configuration.ConfigurationSettings.AppSettings["DSN"];
                SqlConnection Con = new SqlConnection(strCon);
                String SqlCmd = "INSERT INTO ImageStore (ImageData, ImageContentType, ImageDescription, ImageSize) VALUES (@Image, @ContentType, @ImageDescription, @ImageSize)";
                SqlCommand CmdObj = new SqlCommand(SqlCmd, Con);
                CmdObj.Parameters.Add("@Image",SqlDbType.Binary, FileLength).Value = FileByteArray;
                CmdObj.Parameters.Add("@ContentType", SqlDbType.VarChar,50).Value = loFile.PostedFile.ContentType; //记录文件类型
                //把其它单表数据记录上传
                CmdObj.Parameters.Add("@ImageDescription", SqlDbType.VarChar,200).Value = tbDescription.Text;
                //记录文件长度，读取时使用
                CmdObj.Parameters.Add("@ImageSize", SqlDbType.BigInt,8).Value = FileLength;
                Con.Open();
                CmdObj.ExecuteNonQuery(); 
                Con.Close();
                //跳转页面
                Response.Redirect("ShowAll.aspx");
            }
             catch
             {
            }

int  ImgID  =  Convert.ToInt32(Request.QueryString[ " ID " ]);  // ID为图片ID 
             // 建立数据库链接
             string  strCon  =  System.Configuration.ConfigurationSettings.AppSettings[ " DSN " ];
            SqlConnection Con  =   new  SqlConnection(strCon);
            String SqlCmd  =   " SELECT * FROM ImageStore WHERE ImageID = @ImageID " ;
            SqlCommand CmdObj  =   new  SqlCommand(SqlCmd, Con);
            CmdObj.Parameters.Add( " @ImageID " , SqlDbType.Int).Value  =  ImgID;
            Con.Open();
            SqlDataReader SqlReader  =  CmdObj.ExecuteReader();
            SqlReader.Read(); 
            Response.ContentType  =  ( string )SqlReader[ " ImageContentType " ]; // 设定输出文件类型
             // 输出图象文件二进制数制
            Response.OutputStream.Write(( byte [])SqlReader[ " ImageData " ],  0 , ( int )SqlReader[ " ImageSize " ]); 
            Response.End();
             // 也可以保存为图像
//             FileStream fs = new FileStream(@"C:\aa.BMP", FileMode.OpenOrCreate, FileAccess.Write);
//             fs.Write((byte[])SqlReader["ImageData"], 0,(int)SqlReader["ImageSize"]);
//             fs.Close();

            Con.Close();

出现提示框

string  strFile = " F:\\a.doc " ; // 路径根据实际情况而定
if ( ! System.IO.File.Exists(strFile))
    {
    Response.Write("<script language='javascript'>alert('对不起，文件不存在！');</script>");
    return;
   }
   Response.Clear();
   Response.ClearHeaders();
   Response.Charset  =   " GB2312 " ;
   Response.ContentEncoding  = System.Text.Encoding.UTF8;
   Response.ContentType  =   " application/octet-stream " ; 
   FileInfo fi = new  FileInfo(strFile);
   Response.AddHeader( " Content-Disposition " , " attachment;  filename= "    +   HttpUtility.UrlEncode(fi.Name)) ;
   Response.AddHeader( " Content-Length " ,fi.Length.ToString());
    byte [] tmpbyte = new   byte [ 1024 * 8 ];
   FileStream fs = fi.OpenRead();
    int  count;
    while ((count = fs.Read(tmpbyte, 0 ,tmpbyte.Length)) > 0 )
    {
    Response.BinaryWrite(tmpbyte);
    Response.Flush();
   }
   fs.Close();   
   Response.End();

直接在浏览器中打开
    string  strFile = " F:\\a.doc " ; // 路径根据实际情况而定
   Response.Clear();
   Response.ClearHeaders();
   Response.Charset  =   " GB2312 " ;
   Response.ContentEncoding  = System.Text.Encoding.UTF8;
   Response.ContentType  =   " application/msword " ; 
   Response.WriteFile(strFile);

For example:

Response.ContentType  =   " image/jpeg " ;Response.AppendHeader( " Content-Disposition " , " attachment; filename=SailBig.jpg " );Response.TransmitFile( Server.MapPath( " ~/images/sailbig.jpg " ) );Response.End();