Question

I have a fairly unique situation, I have never needed to this before anyways. I have a Linq query that returns data from a database using EF4.1. I want to create multiple similar (same signature) anonymous (or even named if necessary) results from each query result.

Here’s the code i’m using now:

var data = getMyData().Select(x => 
              new 
              {
                GoalName = x.GoalType.Name, 
                Start = x.StartDate, 
                End = x.EndDate, 
                x.StartValue, 
                x.CheckIns
              }).ToList();

var r1 = data.Select(x => 
              new 
              { 
                title = x.GoalName, 
                start = x.Start.ToString(), 
                end = x.End.ToString(), 
                className = "hidden", 
                type = "goal"
              });

var r2 = data.Select(x => 
              new 
              { 
                title = string.Format("Start: {0:0.##}", x.StartValue), 
                start = x.Start.ToString(), 
                end = x.Start.ToString(), 
                className = "", 
                type = "" 
              });

var r3 = data.Select(x => 
              new 
              { 
                title = "End", 
                start = x.End.ToString(), 
                end = x.End.ToString(), 
                className = "", 
                type = "" 
              });

var r4 = data.SelectMany(x => x.CheckIns)
           .Select(y => 
              new 
              { 
                title = y.CheckInValue.Value.ToString(), 
                start = y.CheckInDateTime.ToString(), 
                end = y.CheckInDateTime.ToString(), 
                className = "", 
                type = "" 
              });

var result = r1.Union(r2).Union(r3).Union(r4);

Now maybe this is as good a way as any, but I can’t help feeling that i’m missing something.

Is there a better solution?

Answer 1

What you have is actually OK I think.

But StevenzNPaul’s suggestion not that bad, here’s how you can use the let keyword to store the different projections, then select the results individually (for brevity, I did not project all the fields, but you get the point):

var query = from x in data
            let result1 = new {title = x.GoalName, start = x.Start}
            let result2 = new {title = string.Format("Start: {0:0.##}", x.StartValue), start = x.Start}
            let result3 = new {title = "End", start = x.End}
            let checkins = x.CheckIns.Select(checkin => new { title = "...", start = checkin.Start })
            from result in new[] { result1, result2, result3 }.Concat(checkins)
            select result;

Obviously, whether this is better is a matter of preference. Also, this will result in a different ordering, which may or may not be a problem for you.