public override byte[] ToEsriShape()

// export to binary xml
string binaryXml = multiPatch.ToBinaryXML();

// import from binaryXML - methods need to run on the MCT
Multipatch binaryMultipatch = MultipatchBuilder.FromBinaryXML(binaryXml);

// xml export / import
string xml = multiPatch.ToXML();
Multipatch xmlMultipatch = MultipatchBuilder.FromXML(xml);

// esriShape export/import
byte[] buffer = multiPatch.ToEsriShape();
Multipatch esriPatch = MultipatchBuilder.FromEsriShape(buffer);

// or use GeometryEngine
Multipatch patchImport = GeometryEngine.Instance.ImportFromEsriShape(EsriShapeImportFlags.esriShapeImportDefaults, buffer, multiPatch.SpatialReference) as Multipatch;