SSRS Multivalue lkp

Hi,

I have a situation in SSRS to get the common values between the two columns where the values are sored coma separated as below.

Ex: ColumnA :  abc,cde,efg     ColumnB : cde,xyz,abc    the result in    ColumnC should be : cde,abc

similarly Column A and B will have n number records. I need to right an expression or the Code function to get the required result in ColumnC. I am using SharePoint Lists as Datasource. Cannot write SQL query to achieve this requirement.

Let me know if anybody has an idea. I am completely stuck in this situation.

Thanks