dotnet/wpf · error · ArgumentException

Stream name cannot be

Error message

Stream name cannot be '{0}'.

What it means

StorageInfo.CreateStream rejects the reserved stream name used by EncryptedPackageEnvelope (the encrypted-package marker in Rights-Managed/protected compound documents). Because the name collides with a special package stream, the library throws ArgumentException with the 'Stream name cannot be ...' message.

Solutions

  1. Choose a different stream name that does not match the reserved EncryptedPackageEnvelope.PackageStreamName
  2. Compare the intended name against EncryptedPackageEnvelope.PackageStreamName (case-insensitive) before calling CreateStream
  3. If writing an actual encrypted package, use EncryptedPackageEnvelope APIs instead of raw CreateStream

Example fix

// before
storage.CreateStream(userSuppliedName, CompressionOption.NotCompressed);
// after
if (string.Equals(userSuppliedName, EncryptedPackageEnvelope.PackageStreamName, StringComparison.OrdinalIgnoreCase))
    userSuppliedName = "Content" + userSuppliedName;
storage.CreateStream(userSuppliedName, CompressionOption.NotCompressed);
Defensive patterns

Strategy: validation

Validate before calling

bool reserved = string.Equals(name, EncryptedPackageEnvelope.PackageStreamName, StringComparison.OrdinalIgnoreCase);
if (!reserved) storage.CreateStream(name, CompressionOption.NotCompressed);

Type guard

static bool IsReservedStreamName(string name) => string.Equals(name, EncryptedPackageEnvelope.PackageStreamName, StringComparison.OrdinalIgnoreCase);

Try / catch

try { storage.CreateStream(name, CompressionOption.NotCompressed); }
catch (ArgumentException ex) when (ex.Message.Contains("cannot be")) { /* pick another name */ }

Prevention

When it happens

Trigger: Calling storage.CreateStream with a name equal (case-insensitively) to EncryptedPackageEnvelope.PackageStreamName, e.g. creating a user stream named like the encrypted-package marker.

Common situations: Applications writing custom parts into XPS/OPC compound files that accidentally pick the reserved encrypted-package name; code that derives stream names from user input without filtering reserved names.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/2ef9aee6dc52a12d. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/System/IO/Packaging/CompoundFile/StorageInfo.cs:268

    // public Methods

    /// <summary>
    /// Creates "this" stream
    /// </summary>
    /// <param name="name">Name of stream</param>
    /// <param name="compressionOption">CompressionOptiont</param>
    /// <param name="encryptionOption">EncryptionOption</param>
    /// <returns>Reference to new stream</returns>
    public StreamInfo CreateStream( string name, CompressionOption compressionOption, EncryptionOption encryptionOption )
    {
        CheckDisposedStatus();

        //check the arguments
        ArgumentNullException.ThrowIfNull(name);

        // Stream names: we preserve casing, but do case-insensitive comparison (Native CompoundFile API behavior)
        if (string.Equals(name, EncryptedPackageEnvelope.PackageStreamName, StringComparison.OrdinalIgnoreCase))
            throw new ArgumentException(SR.Format(SR.StreamNameNotValid,name));

        //create a new streaminfo object
        StreamInfo streamInfo = new StreamInfo(this, name, compressionOption, encryptionOption);
        if (streamInfo.InternalExists())
        {
            throw new IOException(SR.StreamAlreadyExist);
        }

        //Define the compression and encryption options in the dataspacemanager
        DataSpaceManager manager = Root.GetDataSpaceManager();
        string dataSpaceLabel = null;
            
        if (manager != null)
        {
            //case : Compression option is set. Stream need to be compressed. Define compression transform.
            //At this time, we only treat CompressionOption - Normal and None. The rest are treated as Normal
            if (compressionOption != CompressionOption.NotCompressed)
            {

View on GitHub (pinned to 81131a70a4)