OpenMcdf is a fully .NET / C# library to manipulate Compound File Binary File Format files, also known as Structured Storage.
Compound files include multiple streams of information (document summary, user data) in a single container, and is used as the bases for many different file formats:
- Microsoft Office (.doc, .xls, .ppt)
- Windows thumbnails cache files (thumbs.db)
- Outlook messages (.msg)
- Visual Studio Solution Options (.suo)
- Advanced Authoring Format (.aaf)
OpenMcdf v3 has a rewritten API and supports:
- An idiomatic dotnet API and exception hierarchy
- Fast and efficient enumeration and manipulation of storages and streams
- File sizes up to 16 TB (using major format version 4 with 4096 byte sectors)
- Transactions (i.e. commit and/or revert)
- Consolidation (i.e. reclamation of space by removing free sectors)
- Nullable attributes
Limitations:
- No support for red-black tree balancing (directory entries are stored in a tree, but are not balanced. i.e. trees are "all-black")
- No support for single writer, multiple readers
To create a new compound file:
byte[] b = new byte[10000];
using var root = RootStorage.Create("test.cfb");
using CfbStream stream = root.CreateStream("MyStream");
stream.Write(b, 0, b.Length);To open an Excel workbook (.xls) and access its main data stream:
using var root = RootStorage.OpenRead("report.xls");
using CfbStream workbookStream = root.OpenStream("Workbook");To create or delete storages and streams:
using var root = RootStorage.Create("test.cfb");
root.CreateStorage("MyStorage");
root.CreateStream("MyStream");
root.Delete("MyStream");For transacted storages, changes can either be committed or reverted:
using var root = RootStorage.Create("test.cfb", StorageModeFlags.Transacted);
root.Commit();
//
root.Revert();A root storage can be consolidated to reduce its on-disk size:
root.Flush(consolidate: true);Support for reading and writing OLE Properties is available via the OpenMcdf.Ole package. However, the API is experimental and subject to change
OlePropertiesContainer co = new(stream);
foreach (OleProperty prop in co.Properties)
{
...
}OpenMcdf runs happily on the Mono platform and multi-targets netstandard2.0 and net8.0 to maximize client compatibility and support modern dotnet features.
