dotnet/wpf · error · ArgumentException

Mode word contains flags that are not valid.

Error message

Mode word contains flags that are not valid.

What it means

XpsFilter.Load converts the STGM mode word into a FileMode. The MODE portion of dwMode is switched on, and only READ/READWRITE are meaningful; CREATE is explicitly rejected with ArgumentException (SR.FilterLoadInvalidModeFlag). A filter is a read-only consumer, so create/truncate-style modes are invalid.

Solutions

1. Pass STGM_READ or STGM_READWRITE in the mode word when calling Load
2. Remove STGM_CREATE (and WRITE/READWRITE+CREATE combinations) from dwMode
3. Use FileAccess.Read-equivalent semantics; filters never create files

Example fix

// before
filter.Load(path, (int)(STGM_FLAGS.CREATE | STGM_FLAGS.READ));
// after
filter.Load(path, (int)STGM_FLAGS.READ);

var mode = (STGM_FLAGS)(dwMode & (int)STGM_FLAGS.MODE);
bool ok = mode == STGM_FLAGS.READ || mode == STGM_FLAGS.READWRITE;

try { filter.Load(path, dwMode); }
catch (ArgumentException ex) { /* bad STGM mode; fix flags */ }

When it happens

Trigger: Calling IPersistFile.Load with dwMode whose STGM MODE bits equal STGM_CREATE (or otherwise land in the CREATE case of the switch).

Common situations: Reusing persistence code written for writable storage to drive the filter; passing STGM_CREATE|STGM_READ out of habit.

Understand the failure class

Background: "unknown output mode", "invalid value for flag", "expects true/false": fixing invalid flag value errors in CLI tools — this error's family across 24 libraries.

Related errors

• File name is null or empty.
• " }} " element found. Expected fixed page element ( }} ).
• ' ' ContentType is not valid.
• ' ' ID is not a valid XSD ID.
• ArgumentNullException

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/feb8af7427e0284e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/IO/Packaging/XpsFilter.cs:366

        /// </param>
        /// <param name="dwMode">The mode in which to open pszFileName. </param>
        void IPersistFile.Load(string pszFileName, int dwMode)
        {
            FileMode fileMode;
            FileAccess fileAccess;
            FileShare fileSharing;

            // Check argument.
            if (pszFileName == null || pszFileName == String.Empty)
            {
                throw new ArgumentException(SR.FileNameNullOrEmpty, nameof(pszFileName));
            }

            // Convert mode information in flag.
            switch ((STGM_FLAGS)(dwMode & (int)STGM_FLAGS.MODE))
            {
                case STGM_FLAGS.CREATE:
                    throw new ArgumentException(SR.FilterLoadInvalidModeFlag, nameof(dwMode));

                default:
                    fileMode = FileMode.Open;
                    break;
            }

            // Convert access flag.
            switch ((STGM_FLAGS)(dwMode & (int)STGM_FLAGS.ACCESS))
            {
                case STGM_FLAGS.READ:
                case STGM_FLAGS.READWRITE:
                    fileAccess = FileAccess.Read;
                    break;

                default:
                    throw new ArgumentException(SR.FilterLoadInvalidModeFlag, nameof(dwMode));
            }

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