how can i pass parameter to linq query

Question

i want to pass parameter to linq query...

public IEnumerable GetPhotos()
{
    PhotoDBDataContext db = new PhotoDBDataContext();
    var query = from p in db.Photos
                orderby p.PhotoId descending
                select new { p.Album, p.AlbumId, p.Description, p.Photographer,
                             p.PhotographerId, p.PhotoId, p.Tags, p.Thumbnail,
                             p.Url };
    return query;
}

in above example "orderby p.PhotoId descending" is used, i want to use parameter in place of p.PhotoId

is it possible...

The `select new { ... }` seems to be fairly comprehensive. Are you really selecting a subset of all columns? If not, you could just write `select p`. — Marcelo Cantos, May 01 '10 at 09:38
See: http://stackoverflow.com/questions/2747114/linq-to-entities-dynamic-sorting/2747641#2747641 — Steven, May 01 '10 at 13:12

Mark Byers · Answer 1 · 2010-05-01T10:23:19.490

3

public IQueryable<Photo> GetPhotos(PhotoDBDataContext db, string orderBy)
{
    var query = from p in db.Photos select p;
    switch (orderBy) {
        case "PhotoId":
            return query.OrderBy(p => p.PhotoId);
        case "AlbumId":
            return query.OrderBy(p => p.AlbumId);
        default:
            // Error handling.
    } 
}

Note that you should not return objects with an anonymous type.

edited May 01 '10 at 10:23

answered May 01 '10 at 09:41

Mark Byers

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can we use lamdaexpression here? – girish May 01 '10 at 09:46

score 1 · Answer 2 · answered May 01 '10 at 10:02

1

With Dynamic Linq, you can write .OrderBy("ColumnName").

answered May 01 '10 at 10:02

fearofawhackplanet

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+1 for the dynamic linq and the 5th use case for DL that I have seen here in the past 24 hours. – Sky Sanders May 01 '10 at 10:32
Yes, there have been quite a lot questions about sorting LINQ queries lately. – Steven May 01 '10 at 13:14

score 0 · Answer 3 · answered Apr 11 '14 at 10:12

You could use an extension. This helped me:

public static class OrderExt
    {
        public static IOrderedQueryable<T> Order<T>(this IQueryable<T> source, string propertyName, SortDirection descending, bool anotherLevel = false)
        {
            var param = Expression.Parameter(typeof(T), string.Empty);
            var property = Expression.PropertyOrField(param, propertyName);
            var sort = Expression.Lambda(property, param);

            var call = Expression.Call(
                typeof(Queryable),
                (!anotherLevel ? "OrderBy" : "ThenBy") +
                (descending == SortDirection.Descending ? "Descending" : string.Empty),
                new[] { typeof(T), property.Type },
                source.Expression,
                Expression.Quote(sort));

            return (IOrderedQueryable<T>)source.Provider.CreateQuery<T>(call);
        }
    }

For full explanation you could go to: http://how-to-code-net.blogspot.ro/2014/04/how-to-call-for-dynamic-orderby-method.html

Nicholas Murray · Answer 4 · 2010-05-01T17:43:17.777

0

You could do it like this if you had two order-by criteria

    public static IQueryable<Photo> GetPhotos(string OrderBy)
    {
        return db.Photos.OrderBy(p => ( (OrderBy == "PhotoId") ? (p.PhotoId) : (p.AlbumId) ));
    }

edited May 01 '10 at 17:43

answered May 01 '10 at 15:25

Nicholas Murray

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how can i pass parameter to linq query

4 Answers4