Category Archives: Development

MS Exchange 2007 Transport Agents

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I haven’t blogged in a while because I have been buried in work writing a new ticketing system based on Exchange 2007 and Outlook 2007. Most of what we’re doing is fairly unexplored (or at least undocumented) territory. For those who have used Event Sinks in previous versions of Exchange, you maybe be happy (or disappointed depending upon your point of view) to find out that Microsoft is deprecating Event Sinks and replacing them with Transport Agents. In my numerous hours scouring the Internet looking for information on how these are implemented, I found just two worthwhile resources:

Transport Agent Tutorial
http://msexchangeteam.com/archive/2006/12/04/431755.aspx

Transport Agent Sample
http://msdn2.microsoft.com/en-us/library/aa579185.aspx

The first is a blog post from a member of the MS Exchange team, on the other is a sample listed in Technet. Furthermore, nearly all code you’ll find regarding Transport Agents in written in C#. While I have nothing against C# and actually come from a Java background, more of our team is familiar with VB.NET and I feel it’s more human readable. According to Microsoft and the Exchange team, “Agents have full access to all messages they process.” You’ll quickly find out that this isn’t the case. Rather, I should say they don’t “easily” have full access rights to all the messages they process. In fact, strangely most of the properties of the message are read-only which posed some particular issues for our development. Luckily, we found a few workarounds that suited our needs for our environment.

You have two basic types of Transport Agents: Smtp Receive agents and Routing agents. A custom Smtp Receive agent will fire on incoming messages to the Smtp server while they would not fire on outgoing messages on our test environment (a single Exchange 2007 Server running in Hub Transport mode). A custom Routing Agent will fire after a Smtp Receive agent and on outgoing messages. Though I haven’t proven this theory, I would also assume that a Smtp Receive agent would fire on messages transmitted to an Edge Transport Exchange 2007 server. You can find a list of available events your agent can call here: http://technet.microsoft.com/en-us/library/e7389d63-3172-40d5-bf53-0d7cd7e78340.aspx. You’ll also notice from this page that Microsoft provides numerous built-in agents to handle various tasks.

One of the first snags I had in trying to get the sample agent from Technet running, was the Namespace. VB.NET does not behave in the same manner as C# when it comes to namespaces. In order to use the install command specified in the Technet article, I had to clear the root namespace:

Screen1

Another big snag we ran into was changing the MessageClass to the our custom form. Thankfully, Yuri from Microsoft was able to provide a workaround: http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=1381211&SiteID=17. I highly recommend using this forum as not only the MVP’s but many of the MS product teams patrol with tons of helpful information.

SQL Update failure with hidden GridView column

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As I’m still fairly new to ASP.NET, I came across what seemed to be a rather simple task that didn’t seem possible. I wanted to use a GridView control to display information from an SQL query and allow the user to edit the values in the GridView control. My update SQL statement included a WHERE clause referencing the primary key, an identity field. While it was not necessary to display the value to the user, it is necessary to reference the value in order to update the underlying data. I added the column to my GridView and marked it as hidden. To my surprise, any changes to the data in Edit mode were not saved. I checked and re-checked my update query and everything looked right. I set the column back to visible and voila, the edit worked properly. After scouring google for a solution and wading through numerous posts that suggested using CSS to hide the data, I finally came across this little blurb in the ASP.NET GridView documentation on the MSDN site:

If the Visible property of a column field is set to false, the column is not displayed in the GridView control and the data for the column does not make a round trip to the client. If you want the data for a column that is not visible to make a round trip, add the field name to the DataKeyNames property.

http://msdn2.microsoft.com/en-us/library/system.web.ui.webcontrols.gridview.datakeynames.aspx

I checked the properties of GridView and surely, no fields were listed in the DataKeyNames property. I added my primary key and removed the column entirely from the GridView. The data was then updated successfully.