C#判断文件的真实类型（非扩展名判断）

public static void CheckTrueFileName()
{
    string path = @"D:\Sheet1.doc";
    System.IO.FileStream fs = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read);
    System.IO.BinaryReader reader = new System.IO.BinaryReader(fs);
    string bx = ""; //文件编码
    byte buffer;
    try
    {
        for(int i=0;i<2;i++)
          {
              bx +=reader.ReadByte().ToString();
          }
        //buffer = reader.ReadByte();
        //bx = buffer.ToString();
        //buffer = reader.ReadByte();
        //bx += buffer.ToString();
    }
    catch (Exception exc)
    {
        Console.WriteLine(exc.Message);
    }
    reader.Close();
    fs.Close();
    //真实的文件类型
    Console.WriteLine(bx);
    //文件名，包括格式
    Console.WriteLine(System.IO.Path.GetFileName(path));
    //文件名， 不包括格式
    Console.WriteLine(System.IO.Path.GetFileNameWithoutExtension(path));
    //文件格式
    Console.WriteLine(System.IO.Path.GetExtension(path));
    Console.ReadLine();
}

下面是关于常用文件类型的编码对照表。

public enum FileExtension
{
    JPG = 255216,
    GIF = 7173,
    BMP = 6677,
    PNG = 13780,
    COM = 7790,
    EXE = 7790,
    DLL = 7790,
    RAR = 8297,
    XML = 6063,
    HTML = 6033,
    ASPX = 239187,
    CS = 117115,
    JS = 119105,
    TXT = 210187,
    SQL = 255254,
    BAT = 64101,
    BTSEED = 10056,
    RDP = 255254,
    PSD = 5666,
    PDF = 3780,
    CHM = 7384,
    LOG = 70105,
    REG = 8269,
    HLP = 6395,
    DOC = 208207,
    XLS = 208207,
    PPT=208207,
    ZIP = 8075,
    DOCX = 8075,
    XLSX = 8075,
    PPTX=8075,
    MMAP=8075,
    CSV=4944
}