Merge pull request #115919 from robinsh/robinsh-0520

Add system names table.

Author: PRMerger15

articles/iot-hub/iot-hub-devguide-messages-construct.md

@@ -66,6 +66,26 @@ For more information about how to encode and decode messages sent using differen
 | user-id |An ID used to specify the origin of messages. When messages are generated by IoT Hub, it is set to `{iot hub name}`. |Yes|
 | iothub-ack |A feedback message generator. This property is used in cloud-to-device messages to request IoT Hub to generate feedback messages as a result of the consumption of the message by the device. Possible values: **none** (default): no feedback message is generated, **positive**: receive a feedback message if the message was completed, **negative**: receive a feedback message if the message expired (or maximum delivery count was reached) without being completed by the device, or **full**: both positive and negative. |Yes|
 
+### System Property Names
+
+The system property names vary based on the endpoint to which the messages are being routed. Please see the table below for details on these names.
+
+
+|System property name|Event Hubs|Azure Storage|Service Bus|Event Grid|
+|--------------------|----------|-------------|-----------|----------|
+|Message ID|message-id|messageId|MessageId|message-id|
+|Iot hub enqueued time|iothub-enqueuedtime|enqueuedTime|iothub-enqueuedtime|iothub-enqueuedtime|
+|User id|user-id|userId|UserId|user-id|
+|Connection device id|iothub-connection-device-id| connectionDeviceId|iothub-connection-device-id|iothub-connection-device-id|
+|Connection module id|iothub-connection-module-id|connectionModuleId|iothub-connection-module-id|iothub-connection-module-id|
+|Connection auth generation id|iothub-connection-auth-generation-id|connectionDeviceGenerationId| iothub-connection-auth-generation-id|iothub-connection-auth-generation-id|
+|Connection auth method|iothub-connection-auth-method|connectionAuthMethod|iothub-connection-auth-method|iothub-connection-auth-method|
+|contentType|content-type|contentType|ContentType|iothub-content-type|
+|contentEncoding|content-encoding|contentEncoding|ContentEncoding|iothub-content-encoding|
+|iothub-enqueuedtime|iothub-enqueuedtime|enqueuedTime|     |iothub-enqueuedtime|
+|iothub-interface-name|iothub-interface-name|interfaceName|Iothub-interface-name|iothub-interface-name|
+|CorrelationId|correlation-id|correlationId|CorrelationId|correlation-id|
+
 ## Message size
 
 IoT Hub measures message size in a protocol-agnostic way, considering only the actual payload. The size in bytes is calculated as the sum of the following values: