DirHelpers.cs

using System;
using System.Runtime.InteropServices;

/// <summary>
/// Class containing methods to retrieve specific file system paths.
/// </summary>
public static class KnownFolders
{
    private static readonly string[] _knownFolderGuids = new string[]
    {
        "{56784854-C6CB-462B-8169-88E350ACB882}", // Contacts
        "{B4BFCC3A-DB2C-424C-B029-7FE99A87C641}", // Desktop
        "{FDD39AD0-238F-46AF-ADB4-6C85480369C7}", // Documents
        "{374DE290-123F-4565-9164-39C4925E467B}", // Downloads
        "{1777F761-68AD-4D8A-87BD-30B759FA33DD}", // Favorites
        "{BFB9D5E0-C6A9-404C-B2B2-AE6DB6AF4968}", // Links
        "{4BD8D571-6D19-48D3-BE97-422220080E43}", // Music
        "{33E28130-4E1E-4676-835A-98395C3BC3BB}", // Pictures
        "{4C5C32FF-BB9D-43B0-B5B4-2D72E54EAAA4}", // SavedGames
        "{7D1D3A04-DEBB-4115-95CF-2F29DA2920DA}", // SavedSearches
        "{18989B1D-99B5-455B-841C-AB7C74E4DDFC}", // Videos
    };

    /// <summary>
    /// Gets the current path to the specified known folder as currently configured. This does
    /// not require the folder to be existent.
    /// </summary>
    /// <param name="knownFolder">The known folder which current path will be returned.</param>
    /// <returns>The default path of the known folder.</returns>
    /// <exception cref="System.Runtime.InteropServices.ExternalException">Thrown if the path
    ///     could not be retrieved.</exception>
    public static string GetPath(KnownFolder knownFolder)
    {
        return GetPath(knownFolder, false);
    }

    /// <summary>
    /// Gets the current path to the specified known folder as currently configured. This does
    /// not require the folder to be existent.
    /// </summary>
    /// <param name="knownFolder">The known folder which current path will be returned.</param>
    /// <param name="defaultUser">Specifies if the paths of the default user (user profile
    ///     template) will be used. This requires administrative rights.</param>
    /// <returns>The default path of the known folder.</returns>
    /// <exception cref="System.Runtime.InteropServices.ExternalException">Thrown if the path
    ///     could not be retrieved.</exception>
    public static string GetPath(KnownFolder knownFolder, bool defaultUser)
    {
        return GetPath(knownFolder, KnownFolderFlags.DontVerify, defaultUser);
    }

    /// <summary>
    /// Gets the default path to the specified known folder. This does not require the folder
    /// to be existent.
    /// </summary>
    /// <param name="knownFolder">The known folder which default path will be returned.</param>
    /// <returns>The current (and possibly redirected) path of the known folder.</returns>
    /// <exception cref="System.Runtime.InteropServices.ExternalException">Thrown if the path
    ///     could not be retrieved.</exception>
    public static string GetDefaultPath(KnownFolder knownFolder)
    {
        return GetDefaultPath(knownFolder, false);
    }

    /// <summary>
    /// Gets the default path to the specified known folder. This does not require the folder
    /// to be existent.
    /// </summary>
    /// <param name="knownFolder">The known folder which default path will be returned.</param>
    /// <param name="defaultUser">Specifies if the paths of the default user (user profile
    ///     template) will be used. This requires administrative rights.</param>
    /// <returns>The current (and possibly redirected) path of the known folder.</returns>
    /// <exception cref="System.Runtime.InteropServices.ExternalException">Thrown if the path
    ///     could not be retrieved.</exception>
    public static string GetDefaultPath(KnownFolder knownFolder, bool defaultUser)
    {
        return GetPath(knownFolder, KnownFolderFlags.DefaultPath | KnownFolderFlags.DontVerify,
            defaultUser);
    }

    /// <summary>
    /// Creates and initializes the known folder.
    /// </summary>
    /// <param name="knownFolder">The known folder which will be initialized.</param>
    /// <exception cref="System.Runtime.InteropServices.ExternalException">Thrown if the known
    ///     folder could not be initialized.</exception>
    public static void Initialize(KnownFolder knownFolder)
    {
        Initialize(knownFolder, false);
    }

    /// <summary>
    /// Creates and initializes the known folder.
    /// </summary>
    /// <param name="knownFolder">The known folder which will be initialized.</param>
    /// <param name="defaultUser">Specifies if the paths of the default user (user profile
    ///     template) will be used. This requires administrative rights.</param>
    /// <exception cref="System.Runtime.InteropServices.ExternalException">Thrown if the known
    ///     folder could not be initialized.</exception>
    public static void Initialize(KnownFolder knownFolder, bool defaultUser)
    {
        GetPath(knownFolder, KnownFolderFlags.Create | KnownFolderFlags.Init, defaultUser);
    }

    private static string GetPath(KnownFolder knownFolder, KnownFolderFlags flags,
        bool defaultUser)
    {
        IntPtr outPath;
        int result = SHGetKnownFolderPath(new Guid(_knownFolderGuids[(int)knownFolder]),
            (uint)flags, new IntPtr(defaultUser ? -1 : 0), out outPath);
        if (result >= 0)
        {
            return Marshal.PtrToStringUni(outPath);
        }
        else
        {
            throw new ExternalException("Unable to retrieve the known folder path. It may not "
                + "be available on this system.", result);
        }
    }

    /// <summary>
    /// Retrieves the full path of a known folder identified by the folder's KnownFolderID.
    /// </summary>
    /// <param name="rfid">A KnownFolderID that identifies the folder.</param>
    /// <param name="dwFlags">Flags that specify special retrieval options. This value can be
    ///     0; otherwise, one or more of the KnownFolderFlag values.</param>
    /// <param name="hToken">An access token that represents a particular user. If this
    ///     parameter is NULL, which is the most common usage, the function requests the known
    ///     folder for the current user. Assigning a value of -1 indicates the Default User.
    ///     The default user profile is duplicated when any new user account is created.
    ///     Note that access to the Default User folders requires administrator privileges.
    ///     </param>
    /// <param name="ppszPath">When this method returns, contains the address of a string that
    ///     specifies the path of the known folder. The returned path does not include a
    ///     trailing backslash.</param>
    /// <returns>Returns S_OK if successful, or an error value otherwise.</returns>
    [DllImport("Shell32.dll")]
    private static extern int SHGetKnownFolderPath(
        [MarshalAs(UnmanagedType.LPStruct)]Guid rfid, uint dwFlags, IntPtr hToken,
        out IntPtr ppszPath);

    [Flags]
    private enum KnownFolderFlags : uint
    {
        SimpleIDList              = 0x00000100,
        NotParentRelative         = 0x00000200,
        DefaultPath               = 0x00000400,
        Init                      = 0x00000800,
        NoAlias                   = 0x00001000,
        DontUnexpand              = 0x00002000,
        DontVerify                = 0x00004000,
        Create                    = 0x00008000,
        NoAppcontainerRedirection = 0x00010000,
        AliasOnly                 = 0x80000000
    }
}

/// <summary>
/// Standard folders registered with the system. These folders are installed with Windows Vista
/// and later operating systems, and a computer will have only folders appropriate to it
/// installed.
/// </summary>
public enum KnownFolder
{
    /// <summary>
    /// The per-user Contacts folder. Introduced in Windows Vista.
    /// Defaults to &quot;%USERPROFILE%\Contacts&quot;.
    /// </summary>
    Contacts,

    /// <summary>
    /// The per-user Desktop folder.
    /// Defaults to &quot;%USERPROFILE%\Desktop&quot;.
    /// </summary>
    Desktop,

    /// <summary>
    /// The per-user Documents folder.
    /// Defaults to &quot;%USERPROFILE%\Documents&quot;.
    /// </summary>
    Documents,

    /// <summary>
    /// The per-user Downloads folder.
    /// Defaults to &quot;%USERPROFILE%\Downloads&quot;.
    /// </summary>
    Downloads,

    /// <summary>
    /// The per-user Favorites folder.
    /// Defaults to &quot;%USERPROFILE%\Favorites&quot;.
    /// </summary>
    Favorites,

    /// <summary>
    /// The per-user Links folder.
    /// Defaults to &quot;%USERPROFILE%\Links&quot;.
    /// </summary>
    Links,

    /// <summary>
    /// The per-user Music folder.
    /// Defaults to &quot;%USERPROFILE%\Music&quot;.
    /// </summary>
    Music,

    /// <summary>
    /// The per-user Pictures folder.
    /// Defaults to &quot;%USERPROFILE%\Pictures&quot;.
    /// </summary>
    Pictures,

    /// <summary>
    /// The per-user Saved Games folder. Introduced in Windows Vista.
    /// Defaults to &quot;%USERPROFILE%\Saved Games&quot;.
    /// </summary>
    SavedGames,

    /// <summary>
    /// The per-user Searches folder.
    /// Defaults to &quot;%USERPROFILE%\Searches&quot;.
    /// </summary>
    SavedSearches,

    /// <summary>
    /// The per-user Videos folder.
    /// Defaults to &quot;%USERPROFILE%\Videos&quot;.
    /// </summary>
    Videos
}