我在traces.customDimensions的特定字段中包含以下json：

当我解析这个Json来提取一个特定的值时，我总是得到一个空列，例如：

traces | order by timestamp desc
| project CurrentContext = parse_json(customDimensions.CurrentPluginContext)
| extend Source = CurrentContext.source
| project Source

查询返回以下内容：

我也试过：

traces | order by timestamp desc
| project timestamp, CurrentContext = customDimensions.CurrentPluginContext, CurrentParentContext = customDimensions.CurrentParentluginContext,
Source = parse_json(tostring(customDimensions.CurrentPluginContext)).source,
DepthCurrentContext = parse_json(tostring(customDimensions.CurrentPluginContext)).depth,
DepthCurrentParentContext = parse_json(tostring(customDimensions.CurrentParentluginContext)).depth
| mv-expand CurrentContext
| extend Source = CurrentContext.source

但是这里我也得到了一个空的"Source"列，而且列"DepthCurrentContext"和"DepthCurrentParentContext"甚至没有出现。

• • Json有效。**

我错过什么了吗？
任何帮助都非常感谢!

• • 2023年2月27日更新**

当我执行以下操作时：

let json = '{"source": "GetUserData","correlationId": "00000000-0000-0000-0000-000000000000","depth": "1","initiatingUserId": "00000000-0000-0000-0000-000000000000","isInTransaction": "False","isolationMode": "2","message": "Update","mode": "Asynchronus","operationId": "00000000-0000-0000-0000-000000000000","orgId": "00000000-0000-0000-0000-000000000000","orgName": "unqXXXXXXXXXXXXXXXXXXXX","requestId": "00000000-0000-0000-0000-000000000000","userId": "00000000-0000-0000-0000-000000000000","entityId": "00000000-0000-0000-0000-000000000000","entityName": "systemuser","type": "Plugin","stage": "Post-operation"}';

traces
| extend properties = parse_json(json)
| project Source = properties.source, CorrelationID = properties.correlationId

我从json中得到属性。json和日志中的ohne完全一样。
你知道吗？