I am attempting to write a custom aggregator to sum TimeSpan values. I kept getting the "No generic method" error so I scoured these forums and pulled down a couple of simple projects to play with. But I'm getting the same error, "No generic method 'Sum' on type 'CustomAggregateFunctionSL.MyAggregates' is compatible with the supplied type arguments and arguments. No type arguments should be provided if the method is non-generic."
Here is a small snippet showing what I'm doing in the page.
And here is the code for the custom aggregator.
What am I doing wrong? I am using 2011.3.1116.1040.