利用Win32API 读取文件头获取Mime-Type

第一个种方式利用Win32API 读取文件头获取Mime-Type

    [DllImport(@"urlmon.dll", CharSet = CharSet.Auto)] 
    private extern static System.UInt32 FindMimeFromData( 
        System.UInt32 pBC, 
        [MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl, 
        [MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer, 
        System.UInt32 cbSize, 
        [MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed, 
        System.UInt32 dwMimeFlags, 
        out System.UInt32 ppwzMimeOut, 
        System.UInt32 dwReserverd 
    );

    public string getMimeFromFile(string filename) 
    { 
        if (!File.Exists(filename)) 
            throw new FileNotFoundException(filename + " not found");

        byte[] buffer = new byte[256]; 
        using (FileStream fs = new FileStream(filename, FileMode.Open)) 
        { 
            if (fs.Length >= 256) 
                fs.Read(buffer, 0, 256); 
            else 
                fs.Read(buffer, 0, (int)fs.Length); 
        } 
        try 
        { 
            System.UInt32 mimetype; 
            FindMimeFromData(0, null, buffer, 256, null, 0, out mimetype, 0); 
            System.IntPtr mimeTypePtr = new IntPtr(mimetype); 
            string mime = Marshal.PtrToStringUni(mimeTypePtr); 
            Marshal.FreeCoTaskMem(mimeTypePtr); 
            return mime; 
        } 
        catch (Exception e) 
        { 
            return "unknown/unknown"; 
        } 
    }

 

第二种方式 利用系统注册表查找Mime-Type

using System.IO;
    using Microsoft.Win32;

    string GetMimeType(FileInfo fileInfo)
    {
        string mimeType = "application/unknown";

        RegistryKey regKey = Registry.ClassesRoot.OpenSubKey(
            fileInfo.Extension.ToLower()
            );

        if(regKey != null)
        {
            object contentType = regKey.GetValue("Content Type");

            if(contentType != null)
                mimeType = contentType.ToString();
        }

        return mimeType;
    }