Linq To SQL OrderBy, issue when using enums

Question

I am having some issues with using the OrderBy extension method on a LINQ query when it is operating on an enum type. I have created a regular DataContext using visual studio by simply dragging and dropping everything onto the designer. I have then created seperate entity models, which are simply POCO's, and I have used a repository pattern to fetch the data from my database and map them into my own entity models (or rather, I have a repository pattern, that builds up and IQueryable that'll do all this).

Everything works just fine, except when I try to apply an OrderBy (outside of the repository) on a property that I have mapped from short/smallint to an enum.

Here are the relevant code bits:

public class Campaign
{
    public long Id { get; set; }
    public string Name { get; set; }
    ....
    public CampaignStatus Status { get; set; }
    ...
}
public enum CampaignStatus : short {
    Active,
    Inactive,
    Todo,
    Hidden
}
public class SqlCampaignRepository : ICampaignRepository
{
...
    public IQueryable<Campaign> Campaigns()
    {
        DataContext db = new DataContext();
        return from c in db.Campaigns
                select new Campaign
                   {
                       Id = c.Id,
                       Name = c.Name,
                       ...
                       Status = (CampaignStatus)c.Status,
                       ...
                   };
     }
}

And then elsewhere

SqlCampaignRepository rep = new SqlCampaignRepository();
var query = rep.Campaigns().OrderBy(c => c.Status);

This triggers the following exception: System.ArgumentException was unhandled by user code Message="The argument 'value' was the wrong type. Expected 'IQMedia.Models.CampaignType'. Actual 'System.Int16'." Source="System.Data.Linq" StackTrace: ved System.Data.Linq.SqlClient.SqlOrderExpression.set_Expression(SqlExpression value) ved System.Data.Linq.SqlClient.SqlBinder.Visitor.VisitSelect(SqlSelect select) ved System.Data.Linq.SqlClient.SqlVisitor.Visit(SqlNode node) ved System.Data.Linq.SqlClient.SqlBinder.Visitor.VisitIncludeScope(SqlIncludeScope scope) ...

(sorry about the danish in there, ved = by/at).

I have tried typecasting the Status to short in the orderBy expression, but that doesn't help it, same if i cast it to the actual enum type as well.

Any help fixing this is greatly appreciated!

Answer 1

Can you specify the type CampaignStatus directly in your DataContext trough the designer? This way the value is automatically mapped to the enum.

Answer 2

What is the relationship between the Campaign class and Campaigns? If Campaigns returns the set of Campaign object, note you can't normally select new a mapped entity.

I wonder if it would work any better if you did the OrderBy before the Select?

One final trick might be to create a fake composable [Function], using trivial TSQL. For example, ABS might be enough. i.e. something like (on the context):

    [Function(Name="ABS", IsComposable=true)] 
    public int Abs(int value) 
    { // to prove not used by our C# code... 
        throw new NotImplementedException(); 
    }

Then try:

  .OrderBy(x => ctx.Abs(x.Status))

I haven't tested the above, but can give it a go later... it works for some other similar cases, though.

Worth a shot...