System.Text.Json和动态解析多态对象

我不相信我会全神贯注于如何正确地使用JsonConverter来解析json结果中的多态性。

I don't believe I am wrapping my head around how to properly use JsonConverter for polymorphism in parsing json results.

在我的场景中，我的目标是TFS中的Git策略配置。一个策略配置：

In my scenario, I am targeting Git Policy Configurations in TFS. A policy configuration:

"value": [
{
        "createdBy": {
            "displayName": "username",
            "url": "url",
            "id": "id",
            "uniqueName": "user",
            "imageUrl": "url"
        },
        "createdDate": "2020-03-21T18:17:24.3240783Z",
        "isEnabled": true,
        "isBlocking": true,
        "isDeleted": false,
        "settings": {
            "minimumApproverCount": 1,
            "creatorVoteCounts": false,
            "allowDownvotes": false,
            "resetOnSourcePush": true,
            "scope": [{
                    "refName": "refs/heads/master",
                    "matchKind": "Exact",
                    "repositoryId": "id"
                }
            ]
        },
        "_links": {
            "self": {
                "href": "url"
            },
            "policyType": {
                "href": "url"
            }
        },
        "revision": 1,
        "id": 974,
        "url": "url",
        "type": {
            "id": "id",
            "url": "url",
            "displayName": "Minimum number of reviewers"
        },
{...}]

更多设置示例：
需要合并策略

More settings examples: Require a Merge Strategy

"settings": {
        "useSquashMerge": true,
        "scope": [
            {
                "refName": "refs/heads/master",
                "matchKind": "Exact",
                "repositoryId": "id"
            }
        ]
    }

必需的审阅者

    "settings": {
        "requiredReviewerIds": [
            "id"
        ],
        "scope": [
            {
                "refName": "refs/heads/master",
                "matchKind": "Exact",
                "repositoryId": "id"
            }
        ]
    }

在上面的json片段中，设置对象根据配置类型而有所不同。

In the json snippet above, the settings object is different based on the type of configuration.

写转换器的最佳方法是可以动态序列化/反序列化设置对象的最佳方法是什么？我已经阅读了几篇关于此的文章，无法完全理解。

What is the best approach to writing a converter than can dynamically serialize/deserialize the settings object? I've read a couple of articles regarding this and can't quite wrap my head around it.

这就是方法我目前正在反序列化我所有的API结果，到目前为止，它们都是简单的结果集。

This is how I am currently deserializing all of my API results, so far they have been simple result sets.

async Task<List<T>> ParseResults<T>( HttpResponseMessage result, string parameter )
{
    List<T> results = new List<T>();

    if ( result.IsSuccessStatusCode )
    {
        using var stream = await result.Content.ReadAsStreamAsync();
        JsonDocument doc = JsonDocument.Parse( stream );
        JsonElement collection = doc.RootElement.GetProperty( parameter ).Clone();

        foreach ( var item in collection.EnumerateArray() )
        {
            results.Add( JsonSerializer.Deserialize<T>( item.ToString() ) );
        }
    }

    return results;
}

我的集成测试。

PolicyConfiguration 是我要反序列化的类型。

PolicyConfiguration is the type I am trying to deserialize to.

[Test]
public async Task Get_TestMasterBranchPolicyConfigurations()
{
    HttpResponseMessage result = await GetResult( $"{_collection}/ProductionBuildTesting/_apis/policy/configurations?api-version=4.1" );

    List<PolicyConfiguration> configurations = await ParseResults<PolicyConfiguration>( result, "value" );
    Assert.AreEqual( 16, configurations.Count );
    JsonPrint( configurations );
}

此解析情况下我目前的班级

My current classes for this parsing situation

public class CreatedBy
{
    [JsonPropertyName( "displayName" )]
    public string DisplayName { get; set; }
    [JsonPropertyName( "url" )]
    public string Url { get; set; }
    [JsonPropertyName( "id" )]
    public Guid Id { get; set; }
    [JsonPropertyName( "uniqueName" )]
    public string UniqueName { get; set; }
    [JsonPropertyName( "imageUrl" )]
    public string ImageUrl { get; set; }
}

public class PolicyConfigurationScope
{
    [JsonPropertyName( "refName" )]
    public string RefName { get; set; }
    [JsonPropertyName( "matchKind" )]
    public string MatchKind { get; set; }
    [JsonPropertyName( "repositoryId" )]
    public Guid RepositoryId { get; set; }
}

public class PolicyConfigurationSettings_MinimumNumberOfReviewers
{
    [JsonPropertyName( "minimumApproverCount" )]
    public int MinimumApproverCount { get; set; }
    [JsonPropertyName( "creatorVoteCounts" )]
    public bool CreatorVoteCounts { get; set; }
    [JsonPropertyName( "allowDownvotes" )]
    public bool AllowDownvotes { get; set; }
    [JsonPropertyName( "resetOnSourcePush" )]
    public bool ResetOnSourcePush { get; set; }
    [JsonPropertyName( "scope" )]
    public List<PolicyConfigurationScope> Scope { get; set; }
}

public class PolicyConfigurationType
{
    [JsonPropertyName( "id" )]
    public Guid Id { get; set; }
    [JsonPropertyName( "url" )]
    public string Url { get; set; }
    [JsonPropertyName( "displayName" )]
    public string DisplayName { get; set; }
}

public class PolicyConfiguration
{
    [JsonPropertyName( "createdBy" )]
    public CreatedBy CreatedBy { get; set; }
    [JsonPropertyName( "createdDate" )]
    public DateTime CreatedDate { get; set; }
    [JsonPropertyName( "isEnabled" )]
    public bool IsEnabled { get; set; }
    [JsonPropertyName( "isBlocking" )]
    public bool IsBlocking { get; set; }
    [JsonPropertyName( "isDeleted" )]
    public bool IsDeleted { get; set; }
    //[JsonPropertyName( "settings" )]
    //public PolicyConfigurationSettings_MinimumNumberOfReviewersSettings Settings { get; set; }
    [JsonPropertyName( "revision" )]
    public int Revision { get; set; }
    [JsonPropertyName( "id" )]
    public int Id { get; set; }
    [JsonPropertyName( "url" )]
    public string Url { get; set; }
    [JsonPropertyName( "type" )]
    public PolicyConfigurationType Type { get; set; }
}