c# - Use Include() method in repository

Question

I have the following with EF 5:

var a = context.Posts.Include(x => x.Pack).Select(x => x.Pack.Id).ToList();

This works. Then I tried to replicate this in my generic repository:

public IQueryable<T> Include<T>(Expression<Func<T, Boolean>> criteria) where T : class
{
    return _context.Set<T>().Include(criteria);
}

But in this case I am not able to do the following:

var b = repository.Include<Post>(x => x.Pack).Select(x => x.Pack.Id).ToList();

I get the error:

Cannot implicitly convert type 'Data.Entities.Pack' to 'bool'

How can I solve this?

What should I change in my Include() method?

Answer 1

Try:

Change

Expression<Func<T, Boolean>> criteria

To

Expression<Func<T, object>> criteria

Edit: To Include multiple entities, you need to add an "include" extension:

public static class IncludeExtension
{
    public static IQueryable<TEntity> Include<TEntity>(this IDbSet<TEntity> dbSet,
                                            params Expression<Func<TEntity, object>>[] includes)
                                            where TEntity : class
    {
        IQueryable<TEntity> query = null;
        foreach (var include in includes)
        {
            query = dbSet.Include(include);
        }

        return query == null ? dbSet : query;
    }
}

Then you can use it like this:

repository.Include(x => x.Pack, x => x.Pack.Roles, ...).Select(x => x.Pack.Id).ToList();

Just make sure "repository" return a "DbSet" Object.