reporting services - SSRS Group By Parameter -

if have report parameter (@fruit) allows multiple selections how can use parameter column group in ssrs matrix?

typically, use parameter in query following:

where tbl.fruit in ( @fruit ) 

then use column in dataset group. however, in case need full dataset returned. can't filter query, still want display groups selected parameter. if query returns apples, oranges , bananas, parameter selects apples , oranges tablix should have 2 columns.

i've tried setting group expression =parameters!fruit.value, error:

the group expression used in grouping ‘columngroup’ returned data type not valid. (rsinvalidexpressiondatatype)

my parameter type text , i've tried , without allowing blank values.

so seems want filter report object based on selected values in multi-value parameter, in case @fruit?

if, say, can't apply filter in dataset query/stored procedure, can apply filter @ tablix level like:

where expression is:

=iif(instr(join(parameters!fruit.value, ","), fields!fruit.value)) > 0   , "include"   , "exclude") 

basically using join function comma-delimted list of selected values, checking if fruit field in object dataset in list; if is, include it.