LINQ Queries with dynamic Order By

Question

I have a query where I need to have ordeby based on a querystring parameter .For example if sortby parameter is price , Query needs to change with price . If its rating than cha

Answer 1

If you know exactly which are all the posible parameters that can be used to order, the Jon´s answer is the best one. But if you have an unknown number of parameters you can build the expression dynamically. e.g:

class Program
{
    static void Main(string[] args)
    {
        var people = new[]{
            new Person { Name = "David", Age = 40 },
            new Person { Name = "Maria", Age = 12 },
            new Person { Name = "Lucas", Age = 45 }
        }.AsQueryable();

        foreach (var p in people.OrderBy("Age"))
        {
            Console.Write(p.Name);
        }
    }

    class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
    }
}

static class IQueryableExtensions
{
    public static IQueryable OrderBy(this IQueryable items, string propertyName)
    {
        var typeOfT = typeof(T);
        var parameter = Expression.Parameter(typeOfT, "parameter");
        var propertyType = typeOfT.GetProperty(propertyName).PropertyType;
        var propertyAccess = Expression.PropertyOrField(parameter, propertyName);
        var orderExpression = Expression.Lambda(propertyAccess, parameter);

        var expression = Expression.Call(typeof(Queryable), "OrderBy", new Type[] { typeOfT, propertyType }, items.Expression, Expression.Quote(orderExpression));
        return items.Provider.CreateQuery(expression);
    }        
}