如何判断一个文件是否是EXCEL?急，在线等！！！

Question

RT,
不能使用扩展名判断，太不靠谱，EXCEL好像没什么公开格式，好像也不能判断MIME，不知道有没有什么其它的方法,WINFORM的。
做为数据库去连接可能是个方法，不过似乎太慢，请各大大指教。

Answer 1

通过文件头：
http://www.dnbcw.com/biancheng/c/hqai113394.html

Answer 2

通过文件头信息判断
MS Word/Excel (xls.or.doc)，文件头：D0CF11E0  

Answer 3

 public static string GetContentTypeByExtName(string extName)
        {
            switch (extName.ToLower())
            {
                case ".001":
                    return "application/x-001";                case ".301":
                    return "application/x-301";                case ".323":
                    return "text/h323";                case ".906":
                    return "application/x-906";                case ".907":
                    return "drawing/907";
.........      ....   
 return "application/x-wrk";                case ".ws":
                    return "application/x-ws";                case ".ws2":
                    return "application/x-ws";                case ".wsc":
                    return "text/scriptlet";                case ".wsdl":
                    return "text/xml";                case ".wvx":
                    return "video/x-ms-wvx";                case ".xdp":
                    return "application/vnd.adobe.xdp";                case ".xdr":
                    return "text/xml";                case ".xfd":
                    return "application/vnd.adobe.xfd";                case ".xfdf":
                    return "application/vnd.adobe.xfdf";                case ".xhtml":
                    return "text/html";                case ".xls":
                    return "application/x-xls";                case ".xlw":
                    return "application/x-xlw";                case ".xml":
                    return "text/xml";                case ".xpl":
                    return "audio/scpls";                case ".xq":
                    return "text/xml";                case ".xql":
                    return "text/xml";                case ".xquery":
                    return "text/xml";                case ".xsd":
                    return "text/xml";                case ".xsl":
                    return "text/xml";                case ".xslt":
                    return "text/xml";                case ".xwd":
                    return "application/x-xwd";                case ".x_b":
                    return "application/x-x_b";                case ".x_t":
                    return "application/x-x_t";
            }
            return "application/octet-stream";
        }

Answer 4

已经搞定，结贴代码：/// <summary>
        /// 是否是EXCEL文件
        /// </summary>
        /// <param name="filePath"></param>
        /// <returns></returns>
        private bool isExcelFile(string filePath)
        {
            FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);
            byte[] b = new byte[4];
            string temstr = "";
            //将文件流读取的文件写入到字节数组
            if (Convert.ToInt32(fs.Length) > 0)
            {
                fs.Read(b, 0, 4);                fs.Close();
                
                for (int i = 0; i < b.Length; i++)
                {
                    temstr += Convert.ToString(b[i], 16);
                }                
            }
         
            if (temstr.ToUpper() == "D0CF11E0")
            { return true; }
            else
            { return false; }
        }