在C# .NET中模拟AWS ScheduledEvent并验证Detail属性问题

问题背景 #

需要验证AWS ScheduledEvent对象的Detail属性数据是否符合要求，该数据来自EventBridge，Detail的JSON结构需与EventBatchData类匹配。EventBatchData类定义如下：

public class EventBatchData
{
    public int BatchSize { get; private set; }
    public int BatchRetries { get; private set; }

    public EventBatchData(int batchSize, int batchRetries)
    {
        BatchSize = batchSize;
        BatchRetries = batchRetries;

        var validator = new EventBatchDataValidator();
        validator.ValidateAndThrow(this);
    }
}

已通过FluentValidation确保EventBatchData不会处于无效状态，但无法直接设置ScheduledEvent.Detail属性，尝试使用dynamic类型赋值失败，测试代码如下：

[Theory]
[AutoFakeItEasyData]
public void NotThrowError_WhenDetailIsValid(EventBatchData eventBatchData)
{
    //Arrange
    dynamic expectedDetail = new ExpandoObject();
    expectedDetail.BatchRetries = eventBatchData.BatchRetries;
    expectedDetail.BatchSize = eventBatchData.BatchSize;

    var scheduledEvent = new ScheduledEvent
    {
        Account = "testAccount",
        Region = "testRegion",
        DetailType = "Scheduled Event",
        Source = "aws.events",
        Time = DateTime.UtcNow,
        Id = "cdc73f9d-aea9-11e3-9d5a-835b769c0d9c",
        Resources = new List<string> { "resource1", "resource2" },
        Detail = expectedDetail
    };

    //Act
    var result = _validator.TestValidate(scheduledEvent);

    //Assert
    result.ShouldHaveValidationErrorFor(x => x.Detail);
}

报错信息 #

无法将类型“System.Dynamic.ExpandoObject”隐式转换为“Amazon.Lambda.CloudWatchEvents.ScheduledEvents.Detail”

解决方案 #

1. 使用泛型版本的ScheduledEvent #

AWS Lambda的ScheduledEvent提供了泛型版本ScheduledEvent<T>，可直接指定Detail的类型为EventBatchData，无需动态类型转换：

[Theory]
[AutoFakeItEasyData]
public void NotThrowError_WhenDetailIsValid(EventBatchData eventBatchData)
{
    //Arrange
    var scheduledEvent = new ScheduledEvent<EventBatchData>
    {
        Account = "testAccount",
        Region = "testRegion",
        DetailType = "Scheduled Event",
        Source = "aws.events",
        Time = DateTime.UtcNow,
        Id = "cdc73f9d-aea9-11e3-9d5a-835b769c0d9c",
        Resources = new List<string> { "resource1", "resource2" },
        Detail = eventBatchData
    };

    //Act
    var result = _validator.TestValidate(scheduledEvent);

    //Assert
    result.ShouldNotHaveValidationErrorFor(x => x.Detail);
}

2. 序列化EventBatchData为JSON再反序列化为Detail #

如果必须使用非泛型ScheduledEvent，可将EventBatchData序列化为JSON字符串，再反序列化为Detail类型：

using System.Text.Json;

[Theory]
[AutoFakeItEasyData]
public void NotThrowError_WhenDetailIsValid(EventBatchData eventBatchData)
{
    //Arrange
    var detailJson = JsonSerializer.Serialize(eventBatchData);
    var detail = JsonSerializer.Deserialize<Detail>(detailJson);

    var scheduledEvent = new ScheduledEvent
    {
        Account = "testAccount",
        Region = "testRegion",
        DetailType = "Scheduled Event",
        Source = "aws.events",
        Time = DateTime.UtcNow,
        Id = "cdc73f9d-aea9-11e3-9d5a-835b769c0d9c",
        Resources = new List<string> { "resource1", "resource2" },
        Detail = detail
    };

    //Act
    var result = _validator.TestValidate(scheduledEvent);

    //Assert
    result.ShouldNotHaveValidationErrorFor(x => x.Detail);
}

3. 直接构造Detail对象并赋值属性 #

Detail类支持动态属性赋值，可直接实例化后设置对应属性：

[Theory]
[AutoFakeItEasyData]
public void NotThrowError_WhenDetailIsValid(EventBatchData eventBatchData)
{
    //Arrange
    var detail = new Detail();
    detail.BatchSize = eventBatchData.BatchSize;
    detail.BatchRetries = eventBatchData.BatchRetries;

    var scheduledEvent = new ScheduledEvent
    {
        Account = "testAccount",
        Region = "testRegion",
        DetailType = "Scheduled Event",
        Source = "aws.events",
        Time = DateTime.UtcNow,
        Id = "cdc73f9d-aea9-11e3-9d5a-835b769c0d9c",
        Resources = new List<string> { "resource1", "resource2" },
        Detail = detail
    };

    //Act
    var result = _validator.TestValidate(scheduledEvent);

    //Assert
    result.ShouldNotHaveValidationErrorFor(x => x.Detail);
}

内容的提问来源于stack exchange，提问作者TortillaCurtain