Query DTO objects through WCF with linq to sql backend

Question

I am working on a project where we need to create complex queries against a WCF service.

The service uses linq to sql at the backend and projects queries to data transfe

Answer 1

If you have long complicated entities then creating a projection by hand is a nightmare. Automapper doesn't work because LINQ cannot use it in conjunction with IQueryable.

This here is the perfect solution : Stop using AutoMapper in your Data Access Code

It will generate a projection 'magically' for you and enable you to run an oData query based on your DTO (data transfer object) class.

    [Queryable]
    public IQueryable GetDatabaseProductDTO(ODataQueryOptions options)
    {
        // _db.DatabaseProducts is an EF table 
        // DatabaseProductDTO is my DTO object
        var projectedDTOs = _db.DatabaseProducts.Project().To();

        var settings = new ODataQuerySettings();
        var results = (IQueryable) options.ApplyTo(projectedDTOs, settings);

        return results.ToArray().AsQueryable();
    }

I run this with

/odata/DatabaseProductDTO?$filter=FreeShipping eq true

Note: this article is from a couple years ago and it's possible that by now AutoMapper has functionality like this built in. I just don't have time I check this myself right now. The inspiration for the above referenced article was based on this article by the author of AutoMapper itself - so it's possible some improved version of it is now included. The general concept seems great and this version is working well for me.