Hello,

From your post, my understanding on this issue is: you wonder how to send
messages, or manipulate host (If I understand it correctly), from the addin
side in the communication pipeline between Host and Add-in. If I'm off
base, please feel free to let me know.

According to the MSDN blog .NET Application Extensibility Part1, 2
http://msdn.microsoft.com/msdnmag/issues/07/02/CLRInsideOut/default.aspx?loc
=en
http://msdn.microsoft.com/msdnmag/issues/07/03/CLRInsideOut/default.aspx
there are three categories of the communication:
1.    The add-in provides a service to the host application. That is to say
Host call Add-in's method
2.    The host offers its behavior to the add-in and lets the add-in define
how it automates the host. In this scenario, the host is really providing a
service to the add-in. Most Microsoft? Office add-ins fall under this
category: upon initialization of the add-in, the Office application will
pass its root object to the add-in, allowing it to automate the host.
3.    add-ins that use the host mainly for screen real-estate rather than any
host-specific functionality

Based on my understanding of your question, I think the 2nd category fits
your request. That is to say, the add-in is able to automate the host
application, like setting data, invoking a host side event, calling a host
side method, etc. Take the Office automation as an example, Office add-ins
are able to manipulate Office documents because Office host passes its
object (Application object) to add-in, and add-in is able to operate the
host using the Application object. Therefore, in order to accomplish your
request, we need to pass the host object to the add-in with a interface
defined in Contract/Adapters/Views. When the add-in get the host object, it
can directly call host's method/event/property to set values, and so on.

Please let me know if I understand you question correctly, or if you have
any other concerns.

Regards,
Jialiang Ge (jialge@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

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