V4 DynamoDb :: DbContext.QueryAsync<T> fails to deserialise List<T>

[alc-aardvark]

Describe the bug

After upgrading my V3 code to V4, I am now getting the following failure.

Logged Exception

System.InvalidOperationException: Unable to convert DynamoDB entry [Amazon.DynamoDBv2.DocumentModel.DynamoDBList] of type Amazon.DynamoDBv2.DocumentModel.DynamoDBList to property Excesses of type System.Collections.Generic.List`1[[IQ.Car.Quote.CarQuoteExcess, IQ.Car.Quote, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.FromDynamoDBEntry(SimplePropertyStorage, DynamoDBEntry, DynamoDBFlatConfig) + 0x3a0
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.PopulateProperty(ItemStorage, DynamoDBFlatConfig, Document, String, PropertyStorage, Object) + 0x6e
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.PopulateInstance(ItemStorage, Object, DynamoDBFlatConfig, StorageConfig) + 0x1b5
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.DocumentToObject(Type, ItemStorage, DynamoDBFlatConfig) + 0xdd
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.FromDynamoDBEntry(SimplePropertyStorage, DynamoDBEntry, DynamoDBFlatConfig) + 0x268
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.PopulateProperty(ItemStorage, DynamoDBFlatConfig, Document, String, PropertyStorage, Object) + 0x6e
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.PopulateInstance(ItemStorage, Object, DynamoDBFlatConfig, StorageConfig) + 0x1b5
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.DocumentToObject(Type, ItemStorage, DynamoDBFlatConfig) + 0xdd
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.DocumentToObject[T](ItemStorage, DynamoDBFlatConfig) + 0x3a
   at Amazon.DynamoDBv2.DataModel.DynamoDBContext.<FromDocumentsHelper>d__65`1.MoveNext() + 0xa2
   at System.Collections.Generic.List`1..ctor(IEnumerable`1) + 0xf1
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1) + 0x43
   at Amazon.DynamoDBv2.DataModel.AsyncSearch`1.<GetRemainingAsync>d__23.MoveNext() + 0x155
--- End of stack trace from previous location ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() + 0x1c
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task) + 0xbe
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task, ConfigureAwaitOptions) + 0x4e
   at IQ.Car.Quote.Database.DynamoDbQuotePersist.<QueryAsyncWithRetry>d__20`1.MoveNext() + 0x228

C# Code

                    CancellationTokenSource cts = new CancellationTokenSource(3 * 1000);
                    results = await DbContext.QueryAsync<T>(hashkey).GetRemainingAsync(cts.Token);

Class structure to be deserialised

     [DynamoDBTable("QuoteResponse")]
    public class QuoteResponse
    {
        public QuoteResponse()
        {
        }


        /// <summary>
        /// Quote Request Id
        /// </summary>
        [DynamoDBHashKey]
        public required string Id { get; init; } 

        /// <summary>
        /// Guid for Quote
        /// </summary>
        [DynamoDBRangeKey]
        public required string Insurer { get; init; }

        /// <summary>
        /// The row is considered "dead" on or after this time (Epoch time)
        ///  - Will be a short time after the expected next heartbeat time
        /// </summary>        
        [DynamoDBProperty("Live")]
        public long LiveTime { get; init; }


        /// <summary>
        /// Vehicle Registration Number
        /// </summary>
        [DynamoDBProperty("CarQuoteResponse")]
        public required CarQuoteResponse CarQuoteResponse { get; init; }
    }

    public class CarQuoteResponse
    {
        public string Insurer { get; set; } = string.Empty;
        public bool Successful { get; set; }
        public long ElapsedMs { get; set; }
        public decimal? TotalAnnual { get; set; }
        public string QuoteRef { get; set; } = string.Empty;
        public string QuoteRefUrl { get; set; } = string.Empty;
        public bool CanEmail { get; set; }
        public bool EmailSent { get; set; }
        public string? AddressText { get; set; }
        public string? VehicleDescription { get; set; }
        public List<CarQuoteExcess> Excesses { get; set; } = new List<CarQuoteExcess>();
        public string FailureReason { get; set; } = string.Empty;
        public bool CanDisplayFailure { get; set; }
}

    public class CarQuoteExcess
    {
        public string Description { get; set; } = string.Empty;
        public decimal? Excess { get; set; }
    }

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

I expect a list of 5 rows to be returned

Current Behavior

under the V4 code it throws an exception when deserialising the data from the dynamodb table. The data in the table looks to be persisted correctly.

Reproduction Steps

I would need to create this if required

Possible Solution

In the V3 code I included an rd.xml file as this is running on AWS Lambda using .Net 8 NativeAOT compilation

Additional Information/Context

Running as AWS Lambda using .Net 8 NativeAOT

AWS .NET SDK and/or Package version used

AWSSDK.Core (4.0.0.8)
AWSSDK.DynamoDBV2 (4.0.1.4)

Targeted .NET Platform

.NET 8 NativeAOT

Operating System and version

Amazon Linux

[alc-aardvark]

Hi Muhammad, I have created a minimal repro of the code zip file attached). If you build it and deploy it to AWS Lambda. You will need to have the DynamoDbb table and correct roles etc. Then create a (public) FunctionUrl for the Lambda. Create rows in the DB with Id of 1234 https://ga6pkfzx6ikcixmuqfuaakwswa0ziyve.lambda-url.ap-southeast-2.on.aws/create/1234 (Try) to read the rows with Id 12345 https://ga6pkfzx6ikcixmuqfuaakwswa0ziyve.lambda-url.ap-southeast-2.on.aws/read/1234 Logged output from this example [cid:c83e816e-a377-4440-abee-91604046a591] Kind regards, Aaron

…

________________________________ From: Muhammad Othman ***@***.***> Sent: Thursday, 12 June 2025 03:57 To: aws/aws-sdk-net ***@***.***> Cc: alc-aardvark ***@***.***>; Mention ***@***.***> Subject: Re: [aws/aws-sdk-net] V4 DynamoDb :: DbContext.QueryAsync<T> fails to deserialise List<T> (Issue #3871) [https://avatars.githubusercontent.com/u/28155926?s=20&v=4]muhammad-othman left a comment (aws/aws-sdk-net#3871)<#3871 (comment)> Hi @alc-aardvark<https://github.com/alc-aardvark>, Thank you for reporting this issue. I’ve tried to reproduce the problem using the setup you described. I inserted the following item into a DynamoDB table using the same model and DynamoDB version, and was able to retrieve it successfully without any issues. image.png (view on web)<https://github.com/user-attachments/assets/5a4f6b9c-d9bb-4aeb-8dcb-2dda29b2bd5f> — Reply to this email directly, view it on GitHub<#3871 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/A46N2DLVUINWUHFDPZTVUKD3DBGVXAVCNFSM6AAAAAB7BZ4H56VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDSNRTGM3DONZWGE>. You are receiving this because you were mentioned.Message ID: ***@***.***>

[alc-aardvark]

Hi Muhammad, Thank you for taking a look. I have sent you a separate email with a minimal reproduction of the problem. Please let me k now if you do not get it. Kind regards, Aaron

…

________________________________ From: Muhammad Othman ***@***.***> Sent: Thursday, June 12, 2025 03:57 To: aws/aws-sdk-net ***@***.***> Cc: alc-aardvark ***@***.***>; Mention ***@***.***> Subject: Re: [aws/aws-sdk-net] V4 DynamoDb :: DbContext.QueryAsync<T> fails to deserialise List<T> (Issue #3871) [https://avatars.githubusercontent.com/u/28155926?s=20&v=4]muhammad-othman left a comment (aws/aws-sdk-net#3871)<#3871 (comment)> Hi @alc-aardvark<https://github.com/alc-aardvark>, Thank you for reporting this issue. I’ve tried to reproduce the problem using the setup you described. I inserted the following item into a DynamoDB table using the same model and DynamoDB version, and was able to retrieve it successfully without any issues. image.png (view on web)<https://github.com/user-attachments/assets/5a4f6b9c-d9bb-4aeb-8dcb-2dda29b2bd5f> — Reply to this email directly, view it on GitHub<#3871 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/A46N2DLVUINWUHFDPZTVUKD3DBGVXAVCNFSM6AAAAAB7BZ4H56VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDSNRTGM3DONZWGE>. You are receiving this because you were mentioned.

[muhammad-othman]

Hi @alc-aardvark ,

Thank you for providing the minimal repro and detailed instructions. I was able to successfully reproduce the issue on my end with the code you shared in the original issue post.

It seems like the problem may be related to trimming. We will investigate this further and let you know what we find.

Best regards,
Muhammad