c# 识别图片格式的方法

bool isJPG = false;
System.Drawing.Image img = System.Drawing.Image.FromFile(filesName)；
if(img.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Jpeg))
{
 isJPG = true;
}

public static FileExtension CheckTextFile(string fileName)
        {
            FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
            System.IO.BinaryReader br = new System.IO.BinaryReader(fs);
            string fileType = string.Empty; ;
            try
            {
                byte data = br.ReadByte();
                fileType += data.ToString();
                data = br.ReadByte();
                fileType += data.ToString();
                FileExtension extension;
                try
                {
                    extension = (FileExtension)Enum.Parse(typeof(FileExtension), fileType);
                }
                catch
                {

                    extension=FileExtension.VALIDFILE
                }
                return extension;
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (fs != null)
                {
                    fs.Close();
                    br.Close();
                }
            }
        }
    }
    public enum FileExtension
    {
        JPG = 255216,
        GIF = 7173,
        PNG = 13780,
        SWF = 6787,
        RAR = 8297,
        ZIP = 8075,
        _7Z = 55122,
        VALIDFILE=9999999
        // 255216 jpg; 

        // 7173 gif; 

        // 6677 bmp, 

        // 13780 png; 

        // 6787 swf 

        // 7790 exe dll, 

        // 8297 rar 

        // 8075 zip 

        // 55122 7z 

        // 6063 xml 

        // 6033 html 

        // 239187 aspx 

        // 117115 cs 

        // 119105 js 

        // 102100 txt 

        // 255254 sql  

    }