How to create an identity column within a lambda?

Question

How can I make the expression add a counter (ID) that is 1,2,3,4 etc... ? I just want to have some unqiue key to identify the data

     var query = data.Select(x =>
            new DemoItemV1
            {
                Id = x.Field<double>("ID"),
                AreaId = x.Field<int>("1Area ID"),
                CategoryTitle = x.Field<string>("2Table Title")
            }).ToList();

take look this one. it shows how to add index in. http://stackoverflow.com/questions/365086/how-to-project-a-line-number-into-linq-query-results — John Liu, Mar 28 '13 at 17:22

score 1 · Accepted Answer · answered Mar 28 '13 at 17:19

I don't think you can do this purely in a Linq-to-Sql or Linq-to-Entities query. But, since you're already materializing it to a list, you can do this:

var query = data.Select(x =>
        new DemoItemV1
        {
            AreaId = x.Field<int>("1Area ID"),
            CategoryTitle = x.Field<string>("2Table Title")
        })
        .AsEnumerable()
        .Select((x, i) => { x.ID = i + 1; return x })
        .ToList();

How to create an identity column within a lambda?

1 Answers1