Whilst writing unit tests for the standard query operators I paid particular attention to how the operators handled special cases of null, containing nulls and empty sets. Most results were as expected and detailed in the table below. 

The situations I think might cause some issues are marked in red. My feelings are that inline aggregate extension methods should give the user the ability to specify a default value rather than throwing an exception that can only be handled by wrapping the entire LINQ over Object expression in a try/catch. 

I would like to see some additional operators that will return the default value rather than an exception:

• MinOrDefault
• MaxOrDefault
• SumOrDefault