Add a column to an IEnumerable in c#

Question

I don't think I can actually add a field (column) to an existing IEnumerable. But what I want is a new IEnumerable that is derived from an existing IEnumerable with a calculated field. The pseudocode in WebMatrix using Web Pages looks like:

var db = Database.Open("LOS");
var ie = db.Query(sqlAssignments);

// make a new ie2 that has an extra field
// ??? ie2 <=== ie with new field c = ie.a + ie.b

var grid = new WebGrid( ie2, extra parameters );

I know how to do this looping through all the rows in ie. But I'm hoping there's something more elegant.

Answer 1

How about:

var ie2 = ie.Select(x => new { x.Foo, x.Bar, Sum = x.Abc + x.Def });
var grid = new WebGrid(ie2);

Answer 2

You can do this using Select. Try this:

ie2 = ie.Select( e => new { IE = e, NewParam =  e.X+e.Y });

Answer 3

ie2 = ie.Select(v => new {v.a, v.b, c = v.a + v.b});

Answer 4

Using Linq!

var newIe = from item in ie
            select new {item.NewField, item.OldFiedl1 etc... }

Also, probably best (if you intend to use outside this method) to make that anonymous type named.

Answer 5

First of all, the IEnumerable is probably a list of something - an object. That is the object you can extend.

You can probably do something like this:

var ie = db.Query( ... );
var ie2 = ie.Select(i => new MyIe2Object {
   Prop1 = i.Prop1,
   NewProp = i.Prop1 + i.Prop2
});