Protobuf-net Append Object Instances into Stream, Deserialize as List

Question

I store multiple instances of a class in a List and when I close my program I save the List into a file using Serialize method.

However, the size of the List can be huge so I wonder if there is a method to Serialize and append object instances into a file during runtime and then Deserialize the file as List when needed.

If there is a way, can you please share an example?

Answer 1

Instead of serializing the entire list, you can add individual instances of the object to the file using the WriteDelimitedTo method.

var persons = new List<Person>();

When adding an element, save it to a file. Note FileMode.Append.

Person person = ...
persons.Add(person);

using (var fileStream = new FileStream("persons.dat", FileMode.Append))
{
    person.WriteDelimitedTo(fileStream);
}

Don't forget to delete or truncate the file before saving first item, if necessary.

---

During deserialization, we read objects one by one using the ParseDelimitedFrom method and add them to the list manually.

using (var fileStream = new FileStream("persons.dat", FileMode.Open))
{
    while (fileStream.Position != fileStream.Length)
    {
        var person = Person.Parser.ParseDelimitedFrom(fileStream);
        persons.Add(person);
    }
}

Don't forget to clear the list before adding items, if necessary.