What causes "'{0}' name is already in use." in dotnet/wpf?

Check storage.GetStorageInfo(name) / existence of a stream with that name before creating the child storage

dotnet/wpf · error · InvalidOperationException

' ' name is already in use.

Error message

'{0}' name is already in use.

What it means

StorageInfo.CoreForChildStorage refuses to create a child storage whose name is already used by a non-storage element (i.e. a stream) in the same parent. The compound file namespace requires storages and streams to occupy distinct names, so it throws InvalidOperationException with the formatted 'name is already in use' message.

Solutions

Check storage.GetStorageInfo(name) / existence of a stream with that name before creating the child storage
Choose a different, unique name for the new storage
Delete or rename the existing stream that occupies the name before creating the storage

Example fix

// before
storage.CreateStorage("Data"); // 'Data' is an existing stream
// after
if (storage.GetStreamInfo("Data") == null)
    storage.CreateStorage("Data");
else
    storage.CreateStorage("DataStorage");

Defensive patterns

Strategy: try-catch

Validate before calling

bool nameFree = storage.GetStreamInfo(name) == null;
if (nameFree) storage.CreateStorage(name);

Type guard

static bool IsFreeStorageName(StorageInfo s, string name) => s.GetStorageInfo(name) == null && s.GetStreamInfo(name) == null;

Try / catch

try { storage.CreateStorage(name); }
catch (InvalidOperationException) { storage.CreateStorage(name + "_storage"); }

Prevention

Remember storages and streams share one case-insensitive namespace
Generate child names from a schema that guarantees uniqueness
Enumerate existing children before bulk-creating structure

When it happens

Trigger: Calling CreateStorage (via BuildStorageInfoRelativeToStorage/CoreForChildStorage) with a name that already identifies a StreamInfo under the same parent storage.

Common situations: Building package structures programmatically where a stream named e.g. 'Data' exists and code then tries to create a storage with the same name; migrating documents between containers with colliding names.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/fa69a92e2f61b3ca. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/System/IO/Packaging/CompoundFile/StorageInfo.cs:169

        BuildStorageInfoRelativeToStorage( parent,  fileName );
    }

    /// <summary>
    /// Respond to a request from a child StorageInfo object to give
    /// it a StorageInfoCore object for the given name.
    /// </summary>
    private StorageInfoCore CoreForChildStorage( string storageNname )
    {
        CheckDisposedStatus();
        
        object childElement = core.elementInfoCores[ storageNname ];

        if( null != childElement &&
            null == childElement as StorageInfoCore )
        {
            // Name is already in use, but not as a StorageInfo
            throw new InvalidOperationException(
                SR.Format(SR.NameAlreadyInUse, storageNname ));
        }
        else if( null == childElement )
        {
            // No such element with the name exist - create one.
            // 
            childElement = new StorageInfoCore( storageNname);
            core.elementInfoCores[ storageNname ] = childElement;
        }

        Debug.Assert( null != childElement as StorageInfoCore,
            "We should have already checked to make sure childElement is either StorageInfoCore, created as one, or thrown an exception if neither is possible");

        return childElement as StorageInfoCore;
    }

    internal StreamInfoCore CoreForChildStream( string streamName )
    {

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