Add dynamic property to Linq result set objects - linq

Question

I have object lists:
List<dynamic> prods = new List<dynamic>();
foreach (DataRow row in dataTable.Rows)
{
dynamic obj = new ExpandoObject();
IDictionary<string, object> oprops = obj;
foreach (System.Data.DataColumn col in dataTable.Columns)
oprops.Add(col.ColumnName, row[col.ColumnName]);
obj = oprops;
list.Add(obj);
}
And pricing list is filled the same way from the DataTable having product pricing.
I have this query:
var result = (from product in prods join price in pricing on product.ID equals price.ProductID select new { product, price }).ToList();
And I want to add some more properties to the result set.
foreach (dynamic obj in q)
{
obj.Test = "yes, testing."; // This line gives runtime error
Console.WriteLine(
"{0} - {1}",
obj.product.Name,
obj.price.UnitPrice);
}
I have some more objects/values to add to the each individual result object in foreach loop.
I am just unable to do that as it throws runtime error as follows:
<>f__AnonymousType1<dynamic,dynamic>' does not contain a definition for 'Test' and no extension method 'Test' accepting a first argument of type '<>f__AnonymousType1<dynamic,dynamic>' could be found (are you missing a using directive or an assembly reference?)

Answer 1

Add the property while querying the data so it is there to set in the foreach loop; eg:
var result = (from product in prods
join price in pricing on product.ID equals price.ProductID
select new { product, price, Test = (string)null, }
).ToList();
or, something I've never tried, maybe use an ExpandoObject:
var result = (from product in prods
join price in pricing on product.ID equals price.ProductID
select new ExpandoObject { product, price }
).ToList();

Answer 2

So, this is what I have found, we cant expand the linq query result set however creating a new exapndo objects solves the problem which enables adding new properties.
This is actually what I did:
List<dynamic> list = new List<dynamic>();
foreach (var o in q)
{
dynamic obj = new ExpandoObject();
IDictionary<string, object> oprops = obj;
oprops.Add("Test", "yes, testing!");
oprops.Add("product", o.product);
oprops.Add("price", o.price);
obj = oprops;
list.Add(obj);
}