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OpenMcdf is a fully .NET / C# library to manipulateCompound File Binary File Format files, also known asStructured 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=newbyte[10000];usingvarroot=RootStorage.Create("test.cfb");usingCfbStreamstream=root.CreateStream("MyStream");stream.Write(b,0,b.Length);

To open an Excel workbook (.xls) and access its main data stream:

usingvarroot=RootStorage.OpenRead("report.xls");usingCfbStreamworkbookStream=root.OpenStream("Workbook");

To create or delete storages and streams:

usingvarroot=RootStorage.Create("test.cfb");root.CreateStorage("MyStorage");root.CreateStream("MyStream");root.Delete("MyStream");

For transacted storages, changes can either be committed or reverted:

usingvarroot=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 writingOLE Properties is available via theOpenMcdf.Ole package. However,the API is experimental and subject to change.

OlePropertiesContainerco=new(stream);foreach(OlePropertypropinco.Properties){  ...}

OpenMcdf runs happily on theMono platform and multi-targetsnetstandard2.0 andnet8.0 to maximize client compatibility and support modern dotnet features.