http://www.sqlservercentral.com/blogs/samvangassql/2011/11/10/_2300_ssrs-error-_1320_-an-item-with-the-same-key-has-already-been-added/ Printed 2016/08/25 12:17AM
#SSRS error – An item with the same key has already been added
Here is a simple yet annoying error I ran into while creating a dataset. Below is the query that I was using and it would run just fine when executed from management studio.
, CalendarMonthNum Mth
, CalendarMonthName Mth
But SSRS doesn’t like those two columns with the same name “Mth” resulting in the error “an item with the same key has already been added”.
To resolve this simply make sure that no two columns in your dataset have the same name.