Can I get the content of a Dictionary using the NrbfDecoder?

Jeroen van den Berg 0

Hi,

I'm following the guide to migrate away from BinaryFormatter. Part of my requirements is that a new version of the application that no longer uses BinaryFormatter will still be able to read payloads generated by the BinaryFormatter. I am trying to use the NrbfDecoder for this, see https://learn.microsoft.com/en-us/dotnet/standard/serialization/binaryformatter-migration-guide/read-nrbf-payloads. It seems to work well with primitive types and classes. But I haven't been able to find a way to read the content of a Dictionary with it. Is this possible? Thanks!

Jiale Xue - MSFT 47,501 Microsoft Vendor

Hi @jeroen van den berg , Welcome to Microsoft Q&A,

BinaryFormatter serializes dictionaries into a special type of object graph. Each key-value pair is serialized as an entry in the graph. NrbfDecoder provides access to these serialized objects through its representation of the payload.

After finding the serialized structure of the dictionary, iterate over its entries and reconstruct the dictionary in your application.

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using Microsoft.IO;

class Program
{
    static void Main()
    {
        // Example: Simulate reading a BinaryFormatter payload with a dictionary
        byte[] payload = GetSerializedBinaryFormatterPayload();

        // Decode the NRBF payload
        using var stream = new MemoryStream(payload);
        var decoder = NrbfDecoder.Decode(stream);

        // Inspect the objects in the decoded graph
        foreach (var record in decoder.Records)
        {
            Console.WriteLine($"Record Type: {record.GetType()}");
        }

        // Assume you locate the dictionary in the graph
        // (manual inspection or automation based on expected structure)
        var dictionary = ReconstructDictionaryFromNrbf(decoder);

        // Use the reconstructed dictionary
        foreach (var kvp in dictionary)
        {
            Console.WriteLine($"{kvp.Key}: {kvp.Value}");
        }
    }

    static Dictionary<object, object> ReconstructDictionaryFromNrbf(NrbfDecoder decoder)
    {
        var result = new Dictionary<object, object>();

        // Pseudo-code: Navigate the decoded structure to locate and extract dictionary entries
        // For each key-value pair record:
        //   result.Add(key, value);

        return result;
    }

    static byte[] GetSerializedBinaryFormatterPayload()
    {
        // Simulate a payload. Replace with your actual payload data.
        using var stream = new MemoryStream();
        var formatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();

        var dictionary = new Dictionary<string, int>
        {
            { "Alice", 30 },
            { "Bob", 25 }
        };

        formatter.Serialize(stream, dictionary);
        return stream.ToArray();
    }
}

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Can I get the content of a Dictionary using the NrbfDecoder?

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