dotnet/wpf · error · FileNotFoundException

STG_E_FILENOTFOUND

STG_E_FILENOTFOUND

Error message

SR.ContainerNotFound

What it means

When opening an existing compound file container, the native StgOpenStorageEx call returned STG_E_FILENOTFOUND, which StorageRoot.Open translates to FileNotFoundException with message ContainerNotFound. The path given does not contain an openable container file.

Solutions

  1. Check File.Exists(path) before opening and correct the path.
  2. Use FileMode.OpenOrCreate or Create when the file may legitimately not exist yet.
  3. Handle FileNotFoundException and surface a user-friendly message.
  4. Ensure the working directory / absolute path is correct.

Example fix

// before
var pkg = Package.Open(path, FileMode.Open, FileAccess.Read); // throws if missing
// after
if (!File.Exists(path))
    throw new FileNotFoundException("Package not found", path);
var pkg = Package.Open(path, FileMode.Open, FileAccess.Read);
Defensive patterns

Strategy: try-catch

Validate before calling

if (!File.Exists(path))
    throw new FileNotFoundException("Package container not found", path);

Type guard

bool ContainerExists(string path) => File.Exists(path);

Try / catch

try { pkg = Package.Open(path, FileMode.Open, FileAccess.Read); }
catch (FileNotFoundException ex) { /* prompt user or create package */ }

Prevention

When it happens

Trigger: Calling StorageRoot.Open / Package.Open with FileMode.Open on a path where no file exists, or the file was deleted/moved between the check and the open.

Common situations: Typos in the package path; relative vs current-directory mismatch; opening an .xlsx/.docx that a prior step failed to write; deleted temp files.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/a8fa7c5a0fcb0fc3. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/System/IO/Packaging/CompoundFile/StorageRoot.cs:352

            // STGM_CREATE not set, call StgOpenStorageEx.
            returnValue = SafeNativeCompoundFileMethods.SafeStgOpenStorageEx(
                path,
                grfMode,
                stgFormatDocFile,
                0,
                IntPtr.Zero,
                IntPtr.Zero,
                ref IID_IStorage,
                out newRootStorage );
        }

        switch( returnValue )
        {
            case SafeNativeCompoundFileConstants.S_OK:
                return StorageRoot.CreateOnIStorage( 
                    newRootStorage );
            case SafeNativeCompoundFileConstants.STG_E_FILENOTFOUND:
                throw new FileNotFoundException( 
                    SR.ContainerNotFound);
            case SafeNativeCompoundFileConstants.STG_E_INVALIDFLAG:
                throw new ArgumentException( 
                    SR.StorageFlagsUnsupported,
                    new COMException(
                        SR.CFAPIFailure, 
                        returnValue));
            default:
                throw new IOException(
                    SR.ContainerCanNotOpen,
                    new COMException(
                        SR.CFAPIFailure, 
                        returnValue));
        }
    }

    /// <summary>
    /// Clean up this container storage instance

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