Создайте MemoryStream из вашего байтового массива и вызовите эту функцию:
public List<Assembly> ExtractAssembliesFromXap(Stream stream) {
List<Assembly> assemblies = new List<Assembly>();
string appManifest = new StreamReader(Application.GetResourceStream(
new StreamResourceInfo(stream, null), new Uri("AppManifest.xaml",
UriKind.Relative)).Stream).ReadToEnd();
XElement deploy = XDocument.Parse(appManifest).Root;
List<XElement> parts = (from assemblyParts in deploy.Elements().Elements()
select assemblyParts).ToList();
foreach (XElement xe in parts) {
string source = xe.Attribute("Source").Value;
AssemblyPart asmPart = new AssemblyPart();
StreamResourceInfo streamInfo = Application.GetResourceStream(
new StreamResourceInfo(stream, "application/binary"),
new Uri(source, UriKind.Relative));
assemblies.Add(asmPart.Load(streamInfo.Stream));
}
return assemblies;
}