SSRS Switch Function error

Hi I am having issue with switch function is ssrs
I have declared a parameter in the report not in the proc
Reportparameter:Sysage,catage,CustomerAge(3 different options to pick at the drop down list)

for the graph i am using two differnt lines but at the category Groups i am using switch function
=Switch("catage Age" = Parameters!ReportParameter1.Value,Fields!catage.Value
,"System Age" =Parameters!ReportParameter1.Value,Fields!SystemAge.Value
,"Customer Age" =Parameters!ReportParameter1.Value,Fields!AccountAge.Value)
It is not picking right drop down list
But instead of Switch Function, if i pick one age like 'catage' it does show the right data

But switch is not picking correctly.

Suggest me how am i doing it wrong.

Thanks in advance