I'm trying to serialize an object and the following SerializationException is thrown:

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> Type 'System.Linq.Enumerable+d\_\_71`1[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]' in Assembly 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable.
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Where is this object in my code? How would I find out? The object graph is fairly large.