判断上传文件类型是否合法(非扩展名)

using System.Collections.Generic;

using System.Web.UI.WebControls;

using System.IO;

namespace Pack.Common

...{

    public enum FileExtension

    ...{

        JPG = 255216,

        GIF =  7173,

        BMP =  6677,

        PNG =  13780

        // 255216 jpg;

        // 7173 gif;

        // 6677 bmp,

        // 13780 png;

        // 7790 exe dll,

        // 8297 rar

        // 6063 xml

        // 6033 html

        // 239187 aspx

        // 117115 cs

        // 119105 js

        // 210187 txt

        //255254 sql 

    }

    public class FileValidation

    ...{

        public static bool IsAllowedExtension(FileUpload fu,FileExtension[] fileEx)

        ...{

            int fileLen = fu.PostedFile.ContentLength;

            byte[] imgArray = new byte[fileLen];

            fu.PostedFile.InputStream.Read(imgArray, 0, fileLen);

            MemoryStream ms = new MemoryStream(imgArray);

            System.IO.BinaryReader br = new System.IO.BinaryReader(ms);

            string fileclass = "";

            byte buffer;

            try

            ...{

                buffer = br.ReadByte();

                fileclass = buffer.ToString();

                buffer = br.ReadByte();

                fileclass += buffer.ToString();

            }

            catch

            ...{

            }

            br.Close();

            ms.Close();

            foreach (FileExtension fe in fileEx)

            ...{

                if (Int32.Parse(fileclass) == (int)fe)

                    return true;

            }

            return false;

        }

    }

}

调用：

Pack.Common.FileExtension[] fe = { Pack.Common.FileExtension.GIF, Pack.Common.FileExtension.JPG };

        if (Pack.Common.FileValidation.IsAllowedExtension(FileUpload1, fe))

        {

            //格式正确

        }