MahApps/MahApps.Metro · error · MahAppsException

The settings file '{filename ?? "<unknown>"}' seems to be co

Error message

The settings file '{filename ?? "<unknown>"}' seems to be corrupted

What it means

Thrown by WindowSettings.Save()/load when deserializing the persisted WindowPlacement setting raises a ConfigurationErrorsException (e.g., the user.config or app settings file is malformed). The code walks the exception chain to find a filename and wraps it in a MahAppsException indicating corruption. The settings file stores window position/size across sessions.

Source

Thrown at src/MahApps.Metro/Controls/WindowSettings.cs:111

        [UserScopedSetting]
        public WindowPlacementSetting? Placement
        {
            get
            {
                try
                {
                    return this[nameof(Placement)] as WindowPlacementSetting;
                }
                catch (ConfigurationErrorsException? ex)
                {
                    string? filename = null;
                    while (ex != null && (filename = ex.Filename) == null)
                    {
                        ex = ex.InnerException as ConfigurationErrorsException;
                    }

                    throw new MahAppsException($"The settings file '{filename ?? "<unknown>"}' seems to be corrupted", ex);
                }
            }
            set => this[nameof(Placement)] = value;
        }

        /// <summary>
        /// Upgrades the application settings on loading.
        /// </summary>
        [UserScopedSetting]
        public bool UpgradeSettings
        {
            get
            {
                try
                {
                    return (this[nameof(UpgradeSettings)] as bool?).GetValueOrDefault(true);
                }
                catch (ConfigurationErrorsException? ex)

View on GitHub (pinned to 72099e310b)

Solutions

1. Delete the corrupted user.config file (typically under %LocalAppData%\<Company\<App\<Version>\user.config) and let the app recreate it.
2. Call ApplicationSettingsBase.Reset() or .Upgrade() after schema changes to migrate old settings.
3. Wrap the settings access in try-catch and fall back to default placement on ConfigurationErrorsException.
4. Ensure settings properties are only added, not renamed/removed, across versions—or implement ISettingsUpgrade.

Example fix

// before
var placement = settings.Placement; // throws MahAppsException

// after
WindowPlacementSetting placement;
try
{
    placement = settings.Placement;
}
catch (MahAppsException)
{
    // settings file corrupted: reset and use defaults
    settings.Reset();
    settings.Save();
    placement = settings.Placement;
}

// Before reading placement, check the settings file exists and is readable
var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal);
if (!config.HasFile)
    return null; // use default placement

WindowPlacementSetting placement;
try
{
    placement = settings.Placement;
}
catch (MahAppsException)
{
    settings.Reset();
    settings.Save();
    placement = settings.Placement;
}

When it happens

Trigger: The user-scoped settings file (user.config) containing persisted WindowPlacement is corrupted—truncated, invalid XML, or schema-mismatched after a version change. The ConfigurationManager throws ConfigurationErrorsException during read, which is caught and rewrapped.

Common situations: App upgraded and the settings schema changed, leaving an incompatible user.config. Machine crashed or disk issue truncated the settings file. Roaming profile conflict writing partial data. First run after a settings property was renamed/removed.

Related errors

• The inverse Flyout theme only works if the window theme abid
• The Dark Flyout theme only works if the window theme abides
• The Light Flyout theme only works if the window theme abides
• {nameof(AutoWatermarkProperty)} is not supported for {fe.Get
• The property 'IsSpellCheckContextMenuEnabled' may only be se

AI-assisted analysis of MahApps/MahApps.Metro@72099e310b (2026-08-13). Data as JSON: /api/errors/1b3d7f87a300ec6d. Report an issue: GitHub.