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Editorial Team
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Asked: 2026-06-09T14:26:38+00:00

Given a Parent and a valid columnName, I want to find all the related

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Given a Parent and a valid columnName, I want to find all the related Children, ordered by a dynamic column name. Here’s how I thought my code would look:

Parent.                                             // EntityObject
Children.                                           // EntityCollection
Where(c => c.Gender == 'm').                        // IEnumerable
OrderBy(columnName, ListSortDirection.Ascending).   // -- not available --
Skip(pages * pageSize).Take(pageSize);

IEnumerable.OrderBy(string columnName) doesn’t exist. Looking around to accomplish the “sort by dynamic column name”, I started with this excellent-looking solution: How do I create an expression tree for run time sorting? , but this operates on an IQueryable

If it did, I assume it would bring the records over the wire to sort and diminish the performance of my pager anyway. So I reordered:

Repository.                                         // Repository
Children.                                           // ObjectSet
Where(c => c.Parent == Parent && c.Gender == 'm').  // ObjectQuery, runtime error
OrderBy(columnName, ListSortDirection.Ascending).   // IOrderedQueryable
Skip(pages * pageSize).Take(pageSize);

ObjectSet and ObjectQuery implement OrderBy(string columnName), and this code compiles, but yields the error:

Unable to create a constant value of type ‘DataModel.Parent’. Only
primitive types (‘such as Int32, String, and Guid’) are supported in
this context.

Of course, I can get the parent ID, but the Child.ParentReference is also a non-primitive type.

I can think of a few ways that would result in loading the entire recordset across the wire, but I feel like I must be missing something, because it must not be so hard to get a set of basic directive through to the database using all MS-centric technologies.

edit: pretend I’m http://en.wikipedia.org/wiki/Quiverfull , and need to paginate my children. 🙂
edit2: clarified my need to query a dynamic column name.

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1 Answer

  1. Editorial Team

    So there were a couple issues I was having, both mentioned in the question title.

    Sorting by a run-time-selected, or dynamic, column name required some expression building. I used @Slace’s popular extension method here.

    That required an IQueryable. IQueryable works for me, because every time I was accidentally transforming my query into an enumerable, I was of course bringing all the results back over the wire before paging, which I was trying to avoid. But I still needed a way to get an IQueryable for results with a relationship to an entity I already held.

    It was something simple I overlooked, just joining on the Entity.Id worked, and didn’t result in redundant joins at the datasource. Not quite as object-oriented as I expected from EF, but it will do.

    Repository.                                         // Repository
Children.                                           // ObjectSet
Where(c => c.Parent.Id == Parent.Id).               // ObjectQuery, works fine
OrderBy(columnName, ListSortDirection.Ascending).   // IOrderedQueryable
Skip(pages * pageSize).Take(pageSize);              // Only transfers 1 page
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