So parameter abc is a multi-valued parameter? Try these, which test the first selected value of abc:

=iif(Parameters!abc.Value(0) =1,False, True)

=iif(Parameters!abc.Value(0) =2, False, True)

I don't know if there's any guarantee on the order of the values when multiple values are selected though.

If you have more complicated logic on which report parts to show I'd imagine the multi-value things get difficult then.

It might be easier to produce a list and have single value parameters, e.g.:

Label Value

Table only 1

Chart Only 2

Matrix Only 3

Table + Chart 4

Matrix + Chart 5

and combine with nested iif statements like for Table:

=iif(Parameters!abcsingle.Value = 1, True, iif(Parameters!abcsingle.Value = 4, True, False))

Cheers