If I have a managed Wix Custom Action, is there anyway I can update a Control with the type of Text? I see that a progress bar can be updated by using the session.Message with InstallMessage.Progress, but I do not see a way for updating other UI.
For a text control you can use a property wrapped in brackets: [SOMEPROP]
Then in your CA you can say session["SOMEPROP"] = "somevalue". Note MSI is wonky about refreshing the UI so you'll pretty much have to transition from one dialog to another to get this to work. In other words, on the next button of the previous dialog call the CA and in the next dialog the text control will display the text.