文件上传

 protected void btnUpload_Click(object sender, EventArgs e)
    {
        if (FileUpload1.HasFile)
        {
            //判断文件大小是否大于10MB  
            if (FileUpload1.PostedFile.ContentLength < 10485760)
            {
                if (CheckFileType())
                {
                    try
                    {
                        /*使用时间戳精确到毫秒,SessionID,上传文件大小, 
                        5位随机数,来做上传文件名唯一性的处理*/
                        /* Random rd = new Random(); 
                         String fileName = DateTime.Now.ToString("yyyyMMddhhmmssfff")+ 
                         rd.Next(10000,99999)+ 
                         Session.SessionID + 
                         FileUpload1.PostedFile.ContentLength + 
                         System.IO.Path.GetExtension(FileUpload1.FileName);*/
                        //string fileName = Guid.NewGuid().ToString() + System.IO.Path.GetExtension(FileUpload1.FileName);
                        /*如果使用时间戳还觉得不够保险,需要绝对唯一 
                         *那么可以使用GUID(全局的唯一标示符):*/

                        String fileName = DateTime.Now.ToString("yyyyMMddhhmmss") +  System.IO.Path.GetExtension(FileUpload1.FileName);
                        string fileSaveFullPath = Server.MapPath("/uploadFiles/") + fileName;
                        if (System.IO.File.Exists(fileSaveFullPath))
                        {
                            lblMessage.Text = "Sorry,the file has existed,please wait for a while to upload!";
                            return;
                        }
                        FileUpload1.PostedFile.SaveAs(fileSaveFullPath);

                        lblMessage.Text = "upload success!";
                        this.Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "redirect", "window.location = window.location;alert('file upload success!')", true);
                    }
                    catch (Exception)
                    {
                        lblMessage.Text = "Exception is appear!";
                    }
                }
                else
                {
                    lblMessage.Text = "sorry,it not allow filename extension !";
                }
            }
            else
            {
                lblMessage.Text = "Sorry,Your file IS beyond 10MB!";
            }
        }
        else
        {
            lblMessage.Text = "Please select a available file!!!";
        }
    }

    //通过读取文件二进制的前两个字节判断文件的类型  
    private bool CheckFileType()
    {
        //得到客户端文件的绝对路径  
        String file = FileUpload1.PostedFile.FileName;

        //创建文件流.  
        System.IO.FileStream fs = new System.IO.FileStream(file, System.IO.FileMode.Open, System.IO.FileAccess.Read);

        //创建读取文件二进制的对象  
        System.IO.BinaryReader br = new System.IO.BinaryReader(fs);

        string fileType = String.Empty;

        //读取文件的第一个字节,并将读取位置提升一个字节.  
        fileType = br.ReadByte().ToString();

        //读取第二个字节,并将读取位置提升一个字节.  
        fileType += br.ReadByte().ToString();

        /*如果不知道文件的二进制前两个字节,可以将它打印出来: 
          Response.Write(fileType);
         */
        Response.Write(fileType);
        System.Collections.Hashtable tmphastable = new System.Collections.Hashtable();
        tmphastable.Add("jpg","25516");
        tmphastable.Add("png","13780");
       tmphastable.Add("gif", "7173");
       tmphastable.Add("bmp", "6677");
       tmphastable.Add("Excel,word,ppt", "208207");
       tmphastable.Add("Access", "01");
       tmphastable.Add("zip", "8075");
       tmphastable.Add("rar", "8297");
        tmphastable.Add("txt", "115115");
        tmphastable.Add("swf", "6787");
        // tmphastable.Add("", "");
        // tmphastable.Add("", "");
        // tmphastable.Add("", "");
        // tmphastable.Add("", "");
        // tmphastable.Add("", "");
        //允许上传文件的扩展名

        bool flag = false;
        foreach( DictionaryEntry tmpDE  in tmphastable)
        {
            if (tmpDE.Value.ToString() == fileType.ToString())
            {
                flag = true;
            }
           
        }
        return flag;
    }