Construction of a parent/child relationship using a single result set exception

[CODEH4RD]

Describe the bug

I have a ASP.NET Core API. When I'm trying to get parent/child results from single dataset from SQL Server stored procedure, I got System.NullReferenceException: "Object reference not set to an instance of an object." error.

Steps to reproduce

1. Dataset

Id	ParentId	Index	Name
1	NULL	1		[{"Key":"en","Value":"Priority 1"}]
2	1		1		[{"Key":"en","Value":"Priority 1 Subpriority 1"}]
3	1		2		[{"Key":"en","Value":"Priority 1 Subpriority 2"}]
4	1		3		[{"Key":"en","Value":"Priority 1 Subpriority 3"}]
7	1		4		[{"Key":"en","Value":"Priority 1 Subpriority 4"}]
8	1		5		[{"Key":"en","Value":"Priority 1 Subpriority 5"}]
9	NULL	2		[{"Key":"en","Value":"Priority 2"}]
11	9		1		[{"Key":"en","Value":"Priority 2 Subpriority 1"}]
12	9		2		[{"Key":"en","Value":"Priority 2 Subpriority 2"}]

2. Model

    public class PriorityModel
    {
        [RecordId]
        public int Id { get; set; }

        [ParentRecordId]
        public int? ParentId { get; set; }

        public int IndexNumber { get; set; }

        [Column(SerializationMode = SerializationMode.Json)]
        public required IEnumerable<LocalizedNameModel> Name { get; set; }

        [ChildRecords]
        public IList<PriorityModel>? Children { get; set; }
    }

    public class LocalizedNameModel
    {
        public required string Key { get; set; }
        public required string Value { get; set; }
    }

3. Controller

        public IActionResult GetPriorities(bool showOnlyTopLevel, bool showAllLanguages, string language = "en")
        {
            using var cnn = new SqlConnection(connectionString);

            var result = cnn.Query("ref.GetPriorities", new { showOnlyTopLevel, showAllLanguages, language },
                Query.Returns(Together<PriorityModel, PriorityModel>.Records));
            return Ok(result);
        }

Expected behavior

I expect following JSON on exit:

[
    {
        "Id": 1,
        "ParentId": null,
        "Index": 1,
        "Name": {
            "Key": "en",
            "Value": "Priority 1"
        },
        "Children": [
            {
                "Id": 2,
                "ParentId": 1,
                "Index": 1,
                "Name": {
                    "Key": "en",
                    "Value": "Priority 1 Subpriority 1"
                },
                "Children": null
            },
            {
                "Id": 3,
                "ParentId": 1,
                "Index": 2,
                "Name": {
                    "Key": "en",
                    "Value": "Priority 1 Subpriority 2"
                },
                "Children": null
            }
        ]
    }
]

• Dotnet version: netcore8.0.12
• Database: SQL Server 2022
• Library version: 8.0.3

[jonwagner]

I don't think there is enough information to reproduce the problem.

Ideally, submit a PR with a failing test case.

But we'll at least need a stack trace and the SQL from your stored procedure.

[CODEH4RD]

I don't think there is enough information to reproduce the problem.

Ideally, submit a PR with a failing test case.

But we'll at least need a stack trace and the SQL from your stored procedure.

It was hard for me :) But I create a project with local database to reproduce this issue. Here's URL for pull request:
CODEH4RD/ParentChildsIssueReproduction#1

Hope, you can help me to solve this problem! Thank you in advance!

[CODEH4RD]

Does my code helps you to reproduce the problem? 🤔