Question

I am importing some data from an file (xls, csv, xml) wich will result in a complex in-memory object graph. Now I need to know whether this graph has been modified since it once was exported. What would be a safe way to check this? I suppose I’d export a hashcode with the file? If so would the standard way of generating an object’s hashcode suffice? How should I generate the hash? I would prefer to generate the hash on the object graph rather than on the actual stream/file.

Answer 1

I ended up doing the following (wich seems to work pretty well):

1. create a custom integer hashcode that include all simple properties of a single object using this algorithm.
2. repeat 1. for all complex objects that this object references
3. serialize all integer hashcode into one binary stream in a well known order
4. create a MD5 checksum of this stream