Dynamic Linq

Hello, please look at my code, I want to set a condition on the linq.

                var dict = (from line in dataNoDups 
                                let columns=line.Split ('\t')
                                select new 
                                {
                                    key=columns[0],
                                    value = columns[0]+'\t'+columns[0]+'\t'+"0"+'\t'+"0"+'\t'+ 1 or 2  or -9                              }).ToDictionary (p=>p.key ,p=>p.value );

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Please note the value needs add "1" or "2" in the last part.
If column[0].StartsWith("Contrl")  then add 1,
If column[0].StartsWith("Case")   then add 2,
otherwise add -9

How to set where clause here?
Thanks.