‘System.String’ must be Xml serializable to be a message part type

Sometimes, when I try to build my project I get the following compile-time error:

‘System.String’ must be Xml serializable to be a message part type — check event log for more information


Despite what the error says – there’s no further information in the event log as it suggests.

I’ve certainly used System.String parts before and it worked just fine, why the error now??


After a couple of hours of chasing my tail around this, I did the only sensible thing to do – I restarted visual studio.

Restarting VS.net it will solve every time. Great!

Author: Sandro Pereira

Sandro Pereira lives in Portugal and works as a consultant at DevScope. In the past years, he has been working on implementing Integration scenarios both on-premises and cloud for various clients, each with different scenarios from a technical point of view, size, and criticality, using Microsoft Azure, Microsoft BizTalk Server and different technologies like AS2, EDI, RosettaNet, SAP, TIBCO etc. He is a regular blogger, international speaker, and technical reviewer of several BizTalk books all focused on Integration. He is also the author of the book “BizTalk Mapping Patterns & Best Practices”. He has been awarded MVP since 2011 for his contributions to the integration community.

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