This should actually be "System.Runtime.CompilerServices.IndexerName" from what I can tell. It appears that there is a typo in the MSDN docs (And elsewhere on the web) unless I'm just totally missing something here... Supposedly its in the mscorlib.dll but I couldnt seem to find a "CSharp" class anywhere under System.Runtime.CompilerServices either in v1.1 or v2.0. And other CSharp classes elsewhere did not contain the "IndexerName" attribute. Weird. The truth is out there...