how to do a sum iff expression for datepart m in last month

Question

I am trying to write an expression to count the number of requests within a specific month from a year's worth of data.

I have tried:

=sum(iif((datepart("M",Fields!RequestDate.Value)) = (datepart("m",Now(-1))),1,0)) 

and many more different versions. Can someone point me in the right direction?

Answer 1

It seems in your example you're counting events from last month? I'm not sure what Now(-1) is trying to calculate in your example.

Anyway, this example worked for me in identifying counts from last month:

=Sum(IIf(DatePart("m", Fields!RequestDate.Value) = DatePart("m", DateAdd("m", -1, Now()))
    , 1
    , 0))

You can update the DateAdd("m", -1, Now()) part of the expression to set the month you want to update against.