C# Windows 10の拡張子の関連付け情報を文字列で取得するコードとクラス

Windows 10ではレジストリに記録される拡張子の関連付け情報が複雑で、レジストリを直接操作すると互換性が失われる可能性があります。shlwapi.dllの公開するAssocQueryStringW関数の使用でこの複雑さや互換性を解決できます。

なお、AssocQueryStringAでAnsi版、IQueryAssociationsの利用でより詳細な情報を取得できます。

using System;
using System.Runtime.InteropServices;
using System.Text;
using Potisan.Windows.Shell;

class Program
{
    static void Main()
    {
        foreach (var name in Enum.GetNames<QueryAssocString.AssocStr>())
        {
            var value = QueryAssocString.Query(
                QueryAssocString.AssocFlags.None,
                Enum.Parse<QueryAssocString.AssocStr>(name),
                @".ps1");
            Console.WriteLine($"{name}: {value}");
        }
        Console.WriteLine();
        /*
        Command:
        Executable: "C:\Program Files\PowerShell\7\pwsh.exe" -NoExit "%1"
        FriendlyDocName: C:\Program Files\PowerShell\7\pwsh.exe
        FriendlyAppName: PS1 ファイル
        NoOpen: pwsh
        ShellNewValue:
        DDECommand:
        DDEIfExec:
        DDEApplication:
        DDETopic: pwsh
        InfoTip: System
        QuickTip: prop:System.ItemTypeText;System.Size;System.DateModified
        TileInfo: prop:System.ItemTypeText;System.Size;System.DateModified
        ContentType: prop:System.ItemTypeText;System.Size;System.DateModified
        DefaultIcon:
        ShellExtension: C:\Program Files\PowerShell\7\pwsh.exe
        DropTarget:
        DelegateExecute:
        SupportedURIProtocols:
        ProgID: file:
        AppID: Applications\pwsh.exe
        AppPublisher:
        AppIconReference: Microsoft Corporation
        Max: C:\Program Files\PowerShell\7\pwsh.exe
        */

        foreach (var name in Enum.GetNames<QueryAssocString.AssocStr>())
        {
            var value = QueryAssocString.Query(
                QueryAssocString.AssocFlags.None,
                Enum.Parse<QueryAssocString.AssocStr>(name),
                @".exe");
            Console.WriteLine($"{name}: {value}");
        }
        /*
        Command:
        Executable: "%1" %*
        FriendlyDocName: %1
        FriendlyAppName: アプリケーション
        NoOpen:
        ShellNewValue:
        DDECommand:
        DDEIfExec:
        DDEApplication:
        DDETopic: %1
        InfoTip: System
        QuickTip: prop:System.FileDescription;System.Company;System.FileVersion;System.DateCreated;System.Size
        TileInfo: prop:System.ItemTypeText;System.Size;System.DateModified
        ContentType: prop:System.FileDescription;System.Company;System.FileVersion;System.DateCreated;System.Size
        DefaultIcon:
        ShellExtension: %1
        DropTarget:
        DelegateExecute:
        SupportedURIProtocols:
        ProgID: file:
        AppID: exefile
        AppPublisher:
        AppIconReference:
        Max: %1
        */
    }
}

namespace Potisan.Windows.Shell
{
    public static class QueryAssocString
    {
        public static string Query(
            AssocFlags flags,
            AssocStr str,
            string assoc,
            string extra = null,
            bool throwsException = false)
        {
            const int ASSOCF_NOTRUNCATE = 0x00000020;

            var hr = NativeMethods.AssocQueryStringW(
                (int)flags,
                (int)str, assoc, extra,
                null, out var bufferSize);
            if (hr < 0)
            {
                if (throwsException) Marshal.ThrowExceptionForHR(hr);
                else return null;
            }

            var buffer = new StringBuilder((int)bufferSize);
            NativeMethods.AssocQueryStringW(
                (int)flags | ASSOCF_NOTRUNCATE,
                (int)str, assoc, extra,
                buffer, out bufferSize);
            if (hr < 0)
            {
                if (throwsException) Marshal.ThrowExceptionForHR(hr);
                else return null;
            }

            return buffer.ToString();
        }

        private static class NativeMethods
        {
            [DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
            public static extern int AssocQueryStringW(
                int flags,
                int str,
                [In] string pszAssoc,
                [In] string pszExtra,
                StringBuilder pszOut,
                out uint pcchOut);
        }

        private const int MAX_PATH = 260;

        public enum AssocFlags : int
        {
            /// <summary>ASSOCF_NONE</summary>
            None = 0x00000000,
            /// <summary>ASSOCF_INIT_NOREMAPCLSID</summary>
            InitNoRemapCLSID = 0x00000001,
            /// <summary>ASSOCF_INIT_BYEXENAME</summary>
            InitByExeName = 0x00000002,
            /// <summary>ASSOCF_OPEN_BYEXENAME</summary>
            OpenByExeName = 0x00000002,
            /// <summary>ASSOCF_INIT_DEFAULTTOSTAR</summary>
            InitDefaultToStar = 0x00000004,
            /// <summary>ASSOCF_INIT_DEFAULTTOFOLDER</summary>
            InitDefaultToFolder = 0x00000008,
            /// <summary>ASSOCF_NOUSERSETTINGS</summary>
            NoUserSettings = 0x00000010,
            // ASSOCF_NOTRUNCATE</summary>
            /// <summary>ASSOCF_VERIFY = 0x00000040,
            Verify = 0x00000040,
            /// <summary>ASSOCF_REMAPRUNDLL</summary>
            RemapRunDLL = 0x00000080,
            /// <summary>ASSOCF_NOFIXUPS</summary>
            NoFixups = 0x00000100,
            /// <summary>ASSOCF_IGNOREBASECLASS</summary>
            IgnoreBaseClass = 0x00000200,
            /// <summary>ASSOCF_INIT_IGNOREUNKNOWN</summary>
            InitIgnoreUnknown = 0x00000400,
            /// <summary>ASSOCF_INIT_FIXED_PROGID</summary>
            InitFixedProgID = 0x00000800,
            /// <summary>ASSOCF_IS_PROTOCOL</summary>
            IsProtocol = 0x00001000,
            /// <summary>ASSOCF_INIT_FOR_FILE</summary>
            InitForFile = 0x00002000
        }

        public enum AssocStr : int
        {
            /// <summary>ASSOCSTR_COMMAND</summary>
            Command,
            /// <summary>ASSOCSTR_EXECUTABLE</summary>
            Executable,
            /// <summary>ASSOCSTR_FRIENDLYDOCNAME</summary>
            FriendlyDocName,
            /// <summary>ASSOCSTR_FRIENDLYAPPNAME</summary>
            FriendlyAppName,
            /// <summary>ASSOCSTR_NOOPEN</summary>
            NoOpen,
            /// <summary>ASSOCSTR_SHELLNEWVALUE</summary>
            ShellNewValue,
            /// <summary>ASSOCSTR_DDECOMMAND</summary>
            DDECommand,
            /// <summary>ASSOCSTR_DDEIFEXEC</summary>
            DDEIfExec,
            /// <summary>ASSOCSTR_DDEAPPLICATION</summary>
            DDEApplication,
            /// <summary>ASSOCSTR_DDETOPIC</summary>
            DDETopic,
            /// <summary>ASSOCSTR_INFOTIP</summary>
            InfoTip,
            /// <summary>ASSOCSTR_QUICKTIP</summary>
            QuickTip,
            /// <summary>ASSOCSTR_TILEINFO</summary>
            TileInfo,
            /// <summary>ASSOCSTR_CONTENTTYPE</summary>
            ContentType,
            /// <summary>ASSOCSTR_DEFAULTICON</summary>
            DefaultIcon,
            /// <summary>ASSOCSTR_SHELLEXTENSION</summary>
            ShellExtension,
            /// <summary>ASSOCSTR_DROPTARGET</summary>
            DropTarget,
            /// <summary>ASSOCSTR_DELEGATEEXECUTE</summary>
            DelegateExecute,
            /// <summary>ASSOCSTR_SUPPORTED_URI_PROTOCOLS</summary>
            SupportedURIProtocols,
            /// <summary>ASSOCSTR_PROGID</summary>
            ProgID,
            /// <summary>ASSOCSTR_APPID</summary>
            AppID,
            /// <summary>ASSOCSTR_APPPUBLISHER</summary>
            AppPublisher,
            /// <summary>ASSOCSTR_APPICONREFERENCE</summary>
            AppIconReference,
            /// <summary>ASSOCSTR_MAX</summary>
            Max
        }
    }
}