I hope someone can help me on this, as I can't find anything relating to my problem.

I am trying to convert some access reports I have done into Reporting Services.
Now in the Access reports it was simple enough to get the total numbers of a field using a filter.
For example getting the total number of people with a gender of female.

When I'm trying to do this within Reporting Services I use the following expression:
Sum(IIf(Fields!gender.Value = "Female", 1, 0))
Now this does return a value, but the result is nowhere near what I get from the query the report is based upon.
When I return the data from the query I get 46 which is correct, yet when I preview the report I get 24.

I even created another query that calculates all of the figures I need using the Cast statement.
This returns one row with all the correct figures, yet simply placing a textbox with an expression equal to the columns value returns 24, yet the value of the column is 46 in the query.

I have spent I while trying to come up with a solution, but I don't know why it is doing this.

Has anyone come across this before?