[SOLVED] Switch statement inside enumeration. How to improve performance?

Issue

I have a list of items that I would like to sort using Linq OrderByDescending.
The sorting is being passed as value to a switch statement.

items.OrderByDescending((SomeObject)i => {
   switch(cond)
   {
      case "conditionA":
        return (float)i.MemberA;
      case "conditionB":
        return (long)i.MemberB;
      case "conditionC":
        return (int)i.MemberB;
   }})

My concern is regarding the performance of this loop.
Is there a way to pre-define the return value and to pass it into the loop once?

Solution

You can move your switch outside OrderByDescending method. Just define a lambda as Func<SomeObject, float> and assign it before linq query:

Func<SomeObject, float> orderBy = null;

switch (cond)
{
    case "conditionA":
        orderBy = i => (float)i.MemberA;
        break;

    case "conditionB":
        orderBy = i => (float)i.MemberB;
        break;

    default:
        orderBy = i => (int)i.MemberC;
        break;
}

Now you can use that lambda in your sorting

var res = items.OrderByDescending(orderBy);

If items is an IQueryable you can change Func<...> to Expression<Func<...>>

Answered By – Aleks Andreev

Answer Checked By – Clifford M. (BugsFixing Volunteer)