Multiple linq query of order by to single one

Question

I have multiple line condition for order by as below

if (enum1)
{
     var = itemlist.orderby(r => r.column1)
}
else if (emum2)
{
     var = itemlist.orderby(r => r.column2)
}

And so on.. Any way to do such thing dynamically.

Answer 1

What you can do is to better manage the column selection for sorting, e.g. using some collection that holds the Func<> for KeySelector.

E.g. if you have a class name 'SomeDTO' with four properties, Prop1,2,3 and 4. And four corresponding enum members.

var searchByMapping = new Dictionary<SearchByEnum,Func<SomeDTO, object>>();
searchByMapping.Add(SearchByEnum.Prop1, x => x.Prop1);
searchByMapping.Add(SearchByEnum.Prop2, x => x.Prop2);
searchByMapping.Add(SearchByEnum.Prop3, x => x.Prop3);

coll = coll.OrderBy(searchByMapping[searchByEnumParam]).ToList();

This is a not so dynamic approach but a typesafe one.

Answer 2

Supposing your enum can have only two values : enum yourEnum( X=0, Y}

enum1 was somewhere set:

itemlist = enum1==Enum.X? itemlist.Orderby(r => r.column1): itemlist.Orderby(r => r.column2)

Answer 3

I did using below extension method.

public static class IQueryableExtensions
    {
        public static IQueryable<T> OrderBy<T>(this IQueryable<T> 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<T>(expression);
        }
    }