how to get sub report Parameters by c#

Question

hi to all

i have a subreport in my main report and it has one storeProcedure as datasource  that has one  sp Parameter like "MyParameter".

i want to get this parameters by c# code ,how can i do this?

in main report we can get paramters using below code but it falling to problem when 

we want to use this code for subreport !!!!!!!

ReportDocument reportDocument;

 reportDocument.Load(pageObject.Server.MapPath(mainreportFilename));

foreach (CrystalDecisions.Shared.ParameterField field in reportDocument.ParameterFields)

//some code 

thanks for any help.