Asp.Net中FileUpload实现文件上传示例

 function checkType(){        
                        
    //得到上传文件的值        
    var fileName=document.getElementById("FileUpLoad1").value;        
                        
    //返回String对象中子字符串最后出现的位置.        
    var seat=fileName.lastIndexOf(".");        
                       
    //返回位于String对象中指定位置的子字符串并转换为小写.        
    var extension=fileName.substring(seat).toLowerCase();        
                       
    //判断允许上传的文件格式        
    //if(extension!=".jpg"&&extension!=".jpeg"&&extension!=".gif"&&extension!=".png"&&extension!=".bmp"){        
    //alert("不支持"+extension+"文件的上传!");        
    //return false;        
    //}else{        
    //return true;        
    //}        
                        
    var allowed=[".jpg",".gif",".png",".bmp",".jpeg"];        
    for(var i=0;i         if(!(allowed[i]!=extension)){        
            return true;        
        }        
    }        
    alert("不支持"+extension+"格式");        
    return false;        
  }

//文件上传按钮click事件      
    protected void btnFileUpload_Click(object sender, EventArgs e)      
    {      
                
        if (FileUpLoad1.HasFile)      
        {      
            //判断文件是否小于10Mb      
            if (FileUpLoad1.PostedFile.ContentLength < 10485760)      
            {      
                try
                {      
                    //上传文件并指定上传目录的路径      
                    FileUpLoad1.PostedFile.SaveAs(Server.MapPath("~/Files/")      
                        + FileUpLoad1.FileName);      
                    /*注意->这里为什么不是:FileUpLoad1.PostedFile.FileName      
                    * 而是:FileUpLoad1.FileName?      
                    * 前者是获得客户端完整限定(客户端完整路径)名称      
                    * 后者FileUpLoad1.FileName只获得文件名.      
                    */
                
                    //当然上传语句也可以这样写(貌似废话):      
                    //FileUpLoad1.SaveAs(@"D:"+FileUpLoad1.FileName);      
                
                    lblMessage.Text = "上传成功!";      
                }      
                catch (Exception ex)      
                {      
                    lblMessage.Text = "出现异常,无法上传!";      
                    //lblMessage.Text += ex.Message;      
                }      
                
            }      
            else
            {      
                lblMessage.Text = "上传文件不能大于10MB!";      
            }      
        }      
        else
        {      
            lblMessage.Text = "尚未选择文件!";      
        }      
    }

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);*/
            
                        /*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 = Guid.NewGuid().ToString() + System.IO.Path.GetExtension(FileUpload1.FileName);    
                                    
                        FileUpload1.PostedFile.SaveAs(Server.MapPath("~/Files/") + fileName);    
            
                        lblMessage.Text = "上传文件成功!";    
                    }    
                    catch (Exception)    
                    {    
                        lblMessage.Text = "出现异常无法上传!";    
                    }    
                }    
                else
                {    
                    lblMessage.Text = "不支持此文件格式!";    
                }    
            }    
            else
            {    
                lblMessage.Text = "文件大小不能超过10MB";    
            }    
        }    
        else
        {    
            lblMessage.Text = "文件不存在,请选择文件!";    
        }    
    }    
            
    //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(fileBinary);    
         */
            
        //允许上传文件的扩展名    
        String[] allowtedExtension = {"255216", "7173", "6677"};    
            
        //判断是否允许上传的文件类型    
        foreach (string allowEx in allowtedExtension)    
        {    
            if (!(allowEx != fileType))    
            {    
                return true;    
            }    
        }    
        return false;    
    }