asp.net 判断上传文件的类型 【2016-04-04 00:39更新】

asp.net 判断上传文件的类型

.NET

172 2016/4/4 00:29

asp.net 判断上传文件的类型


        /// <summary>

        /// 文件上传判断类型

        /// </summary>

        /// <param name="sender"></param>

        /// <param name="e"></param>

        protected void btnUpload_Click(objectsender, EventArgs e)

        {

            #region 一、 安全性比较低,把文本文件1.txt改成1.jpg照样可以上传,但其实现方法容易理解,实现也简单,所以网上很多还是采取这种方法。

            Boolean fileOk = false;

            string path = Server.MapPath("~/images/");

            //判断是否已经选取文件

            if (FileUpload1.HasFile)

            {

                //取得文件的扩展名,并转换成小写

                string fileExtension = System.IO.Path.GetExtension(FileUpload1.FileName).ToLower();

                //限定只能上传jpggif图片

                string[] allowExtension = { ".jpg", ".gif" };

                //对上传的文件的类型进行一个个匹对

                int j = 0;

                for (int i = 0; i < allowExtension.Length; i++)

                {

                    if (fileExtension == allowExtension[i])

                    {

                        fileOk = true;

                        return;

                    }

                    else

                    {

                        j++;

                    }

                }

                if (j > 0)

                {

                    Response.Write("<script>alert('文件格式不正确');</script>");

                    return;

                }

            }

            else

            {

                Response.Write("<script>alert('你还没有选择文件');</script>");

                return;

            }

            //如果扩展名符合条件,则上传

            if (fileOk)

            {

                FileUpload1.PostedFile.SaveAs(path + FileUpload1.FileName);

                Response.Write("<script>alert('上传成功');</script>");

            }

            #endregion

            #region  二、不检测文件后缀而是检测文件MIME内容类型。

            Boolean fileOk = false;

            string path = Server.MapPath("~/images/");

            //判断是否已经选取文件

            if (FileUpload1.HasFile)

            {

                //取得文件MIME内容类型

                string type = this.FileUpload1.PostedFile.ContentType.ToLower();

                if (type.Contains("image"))    //图片的MIME类型为"image/xxx",这里只判断是否图片。

                {

                    fileOk = true;

 

                }

                else

                {

                    Response.Write("<script>alert('格式不正确')</script>");

                }

            }

            else

            {

                Response.Write("<script>alert('你还没有选择文件');</script>");

            }

            //如果扩展名符合条件,则上传

            if (fileOk)

            {

                FileUpload1.PostedFile.SaveAs(path + FileUpload1.FileName);

                Response.Write("<script>alert('上传成功');</script>");

            }

            #endregion

 #region 可以实现真正意义上的文件类型判断。

            try

            {

                //判断是否已经选取文件

                if (FileUpload1.HasFile)

                {

                    if (IsAllowedExtension(FileUpload1))

                    {

                        string path = Server.MapPath("~/images/");

                        FileUpload1.PostedFile.SaveAs(path + FileUpload1.FileName);

                        Response.Write("<script>alert('上传成功');</script>");

                    }

                    else

                    {

                        Response.Write("<script>alert('您只能上传jpg或者gif图片');</script>");

                    }

 

                }

                else

                {

                    Response.Write("<script>alert('你还没有选择文件');</script>");

                }

            }

            catch (Exception error)

            {

                Response.Write(error.ToString());

            }

            #endregion

        } 

    }

       //真正判断文件类型的关键函数

        public static bool IsAllowedExtension(FileUpload hifile)

        {

            System.IO.FileStream fs = new System.IO.FileStream(hifile.PostedFile.FileName, System.IO.FileMode.Open, System.IO.FileAccess.Read);

            System.IO.BinaryReader r = new System.IO.BinaryReader(fs);

            string fileclass = "";

            //这里的位长要具体判断.

            byte buffer;

            try

            {

                buffer = r.ReadByte();

                fileclass = buffer.ToString();

                buffer = r.ReadByte();

                fileclass += buffer.ToString();

 

            }

            catch

            {

 

            }

            r.Close();

            fs.Close();

            if (fileclass == "255216" || fileclass == "7173")//说明255216jpg;7173gif;6677BMP,13780PNG;7790exe,8297rar

            {

                return true;

            }

            else

            {

                return false;

            }

        }

作者:望月狼

出处:http://www.cnblogs.com/wangyuelang0526

 


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