how can i pass parameter to linq query - linq-to-sql

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...

Answer 1

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.

Answer 2

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

Answer 3

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) ));
}

Answer 4

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