Convert arraylist object to byte[]

I have araylist object named list, here i want to convert my arraylist object to byte[], while doing the below coding its giving an error: "At least one element in the source array could not be cast down to the destination arraytype"
my coding:

 byte[] obj= new byte[list.Count];
      list.CopyTo(obj); 
 

here my array list objects returns report data from ssrs reports.what i want to do here to solve this issue.

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