You're implementing an activity handler for a message received event. How can your code access the text of the message that was received?

The best way to access the text of the message that was received in an activity handler is through the turn context. The turn context in the Microsoft Bot Framework is an object that contains information about the current activity, including the message payload. This context allows access to various properties of the activity, such as the text of the message, the sender's information, and the conversation details.

When a message is received, the activity will typically contain a property called 'text' or 'value' that holds the actual content of the message. By using the turn context, your code can easily retrieve this information and perform necessary actions based on the message content.

The other options involve different aspects of bot development. Implementing a waterfall dialog does not directly give access to the message text; instead, it provides a structured way to handle user interactions over multiple turns. The reference to the previous member added activity does not pertain to accessing the current message text but rather to previous activities in the conversation or certain context-specific references. Lastly, user data storage pertains to persistently storing user-specific information rather than directly accessing a message from the current turn.