Saving nested items with class hierarchies

[atjohns]

Describe the bug

This is a similar issue to a very old discussion posted here on class hierarchies in Dynamo, but this one is explicitly about saving items. I am trying to use DynamoDB to save a model that mimics the following structure

    public class A
    {
        public string Name { get; set; }

        public int MyPropA { get; set; } = 1;
    }

    public class B : A
    {
        public int MyPropB { get; set; } = 2;
    }

    [DynamoDBTable("Test")]
    public class ModelA
    {
        [DynamoDBHashKey]
        public Guid id { get; set; }

        public List<A> MyClasses { get; set; }
    }

If we instantiate a new instance of this model like so...

            var a1 = new A { Name = "A1" };
            var b1 = new B { Name = "B1" };

            Guid id = Guid.NewGuid();

            var model = new ModelA
            {
                id = id,
                MyClasses = new List<A> { a1, b1 }
            };

We end up with a list that contains both Class B & Class A types that are being saved into Dynamo incorrectly.

Expected Behavior

Expectation would be for both Model A & Model B to save with the properties that are pushed by the code and be able to recognize the Model B inheritance

Current Behavior

When this model is saved to Dynamo it only saves the Class A properties. Here's a screenshot showing what the object looks like when the Save call is made vs what it looks like within Dynamo

Reproduction Steps

See above

Possible Solution

No response

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

AWSSDK.DynamoDBv2 3.7.104

Targeted .NET Platform

.NET 7

Operating System and version

Windows 10

[ashishdhingra]

Reproducible using below code:

using System;
using System.Collections.Generic;
using Amazon.DynamoDBv2;
using Amazon.DynamoDBv2.DataModel;
using Amazon.Runtime;

using (AmazonDynamoDBClient client = new AmazonDynamoDBClient())
{
    DynamoDBContext context = new DynamoDBContext(client);
    var a1 = new A { Name = "A1" };
    var b1 = new B { Name = "B1" };

    Guid id = Guid.NewGuid();

    var model = new ModelA
    {
        id = id,
        MyClasses = new List<A> { a1, b1 }
    };

    await context.SaveAsync(model);
}



public class A
{
    public string Name { get; set; }

    public int MyPropA { get; set; } = 1;
}

public class B : A
{
    public int MyPropB { get; set; } = 2;
}

[DynamoDBTable("Test")]
public class ModelA
{
    [DynamoDBHashKey]
    public Guid id { get; set; }

    public List<A> MyClasses { get; set; }
}

Unsure if this is by design due to limitation mentioned in #245 (comment). Needs review with the team.

[bykka]

Looks like it a common issue for dynamoDB sdk of different languages.
At least java version discuss the same problem
aws/aws-sdk-java-v2#2861
I guess would be nice to have the similar implementation for simpler code migration

[dscpinheiro]

This has been released in the latest preview of V4: https://www.nuget.org/packages/AWSSDK.DynamoDBv2/4.0.0-preview.9

Thanks again @irina-herciu for the contribution!