Dynamic Order (SQL ORDERBY) in LINQ CompiledQuery

Question

Hello, how can I create a dynamic ORDERBY in my LINQ CompiledQuery (e.g. supply Order Field and Direction as parameters for the compiled query)?

Answer 1

I think I found it:

Check out this link. It will point you to the VS2008 code samples which contains a Dynamic Linq Query Library which contains the extension method below. This will allow you to go:

Object.OrderBy("ColumnName");

Here is the extension methods, but you may want the whole library.

public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string ordering, params object[] values) {
    return (IQueryable<T>)OrderBy((IQueryable)source, ordering, values);
}

public static IQueryable OrderBy(this IQueryable source, string ordering, params object[] values) {
    if (source == null) throw new ArgumentNullException("source");
    if (ordering == null) throw new ArgumentNullException("ordering");
    ParameterExpression[] parameters = new ParameterExpression[] {
        Expression.Parameter(source.ElementType, "") };
    ExpressionParser parser = new ExpressionParser(parameters, ordering, values);
    IEnumerable<DynamicOrdering> orderings = parser.ParseOrdering();
    Expression queryExpr = source.Expression;
    string methodAsc = "OrderBy";
    string methodDesc = "OrderByDescending";
    foreach (DynamicOrdering o in orderings) {
        queryExpr = Expression.Call(
            typeof(Queryable), o.Ascending ? methodAsc : methodDesc,
            new Type[] { source.ElementType, o.Selector.Type },
            queryExpr, Expression.Quote(Expression.Lambda(o.Selector, parameters)));
        methodAsc = "ThenBy";
        methodDesc = "ThenByDescending";
    }
    return source.Provider.CreateQuery(queryExpr);
}