c# - Using Linq to return a Comma separated string -

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i have class in application

public class productinfo {   public int productid {get;set;}   public int producttype{get;set;} }

i want write linq query can return me list of productids in comma separated format producttype equal number ?

i tried using string.join linq statement didn't seem work.

var s = string.join(",", products.where(p => p.producttype == sometype)                                  .select(p => p.productid.tostring()));

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