Modify Extension Method To Allow ThenBy

Question

I have the following custom extension method, which allows you to dynamically specify which field will be sorted - it is used to tie into a JQuery DataTable.

public static IQueryable<T> OrderByField<T>(this IQueryable<T> q, string SortField, string SortDirection)
{

  var param = Expression.Parameter(typeof(T), "p");
  var prop = Expression.Property(param, SortField);
  var exp = Expression.Lambda(prop, param);

  var method = SortDirection == "asc" ? "OrderBy" : "OrderByDescending";

  var types = new Type[] { q.ElementType, exp.Body.Type };
  var mce = Expression.Call(typeof(Queryable), method, types, q.Expression, exp);

  return q.Provider.CreateQuery<T>(mce);

}

It is then called as follows: .OrderByField("ColumnName", "asc") where the two params are strings.

I wish to modify this function to allow "thenby" to be called immediately after, however I am unsure how to do this.

Any help greatly appreciated.

The values are populated directly from an AJAX request. Can MVC bind to an enum? — Gavin Coates, Jan 04 '15 at 19:14
Make sure to also look at the more recent answers of the duplicate. — Gert Arnold, Jan 04 '15 at 22:40

score 0 · Answer 1 · answered Jan 04 '15 at 16:50

0

You can call OrderBy() or OrderByDescending() directly (not through CreateQuery()), then return the IOrderedQueryable<T>.

answered Jan 04 '15 at 16:50

SLaks

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how would you go about doing this though, OrderBy doesn't have an override that allows you to pass the field name as a string. – Gavin Coates Jan 04 '15 at 19:12
@GavinCoates: You need to pass it an `Expression>`. You may need Reflection to invoke it generically. – SLaks Jan 04 '15 at 19:20
Can you demonstrate how to do that? – Gavin Coates Jan 05 '15 at 16:14

Modify Extension Method To Allow ThenBy

1 Answers1