LINQ to SQL: Reusable expression for property?
- by coenvdwel
Pardon me for being unable to phrase the title more exact.
Basically, I have three LINQ objects linked to tables. One is Product, the other is Company and the last is a mapping table Mapping to store what Company sells which products and by which ID this Company refers to this Product.
I am now retrieving a list of products as follows:
var options = new DataLoadOptions();
options.LoadWith<Product>(p => p.Mappings);
context.LoadOptions = options;
var products = (
from p in context.Products
select new {
ProductID = p.ProductID,
//BackendProductID = p.BackendProductID,
BackendProductID = (p.Mappings.Count == 0)
? "None"
: (p.Mappings.Count > 1)
? "Multiple"
: p.Mappings.First().BackendProductID,
Description = p.Description
}
).ToList();
This does a single query retrieving the information I want. But I want to be able to move the logic behind the BackendProductID into the LINQ object so I can use the commented line instead of the annoyingly nested ternary operator statements for neatness and re-usability.
So I added the following property to the Product object:
public string BackendProductID
{
get
{
if (Mappings.Count == 0) return "None";
if (Mappings.Count > 1) return "Multiple";
return Mappings.First().BackendProductID;
}
}
The list is still the same, but it now does a query for every single Product to get it's BackendProductID. The code is neater and re-usable, but the performance now is terrible.
What I need is some kind of Expression or Delegate but I couldn't get my head around writing one. It always ended up querying for every single product, still.
Any help would be appreciated!
