LiNQ在OrderBy之后使用ThenBy

Question

I have a collection and number of OrderBy statemensts which sorts using query.Sort parameter

switch (filters.Sort)
{
    case "new":
        query = query.OrderByDescending(a => a.CreatedAt);
        break;
    case "old":
        query = query.OrderBy(a => a.CreatedAt);
        break;
    case "salary-asc":
        query = query.OrderBy(a => a.Profile.CompensationTypeRate.FromCompensation);
}

Now I need to apply another sort using a query.Grade parameter. I know I should be using ThenBy to have multiple Order statements, but in this case I cannot write it in one line.

Is there a way to write OrderBy and ThenBy so they are executed one by one, and not in one line?

Or can I create some anonymous function that contains my OrderBy and ThenBy conditions ?

Answer 1

You can do it in two parts if you use a variable of type IOrderedQueryable<T> - that's what enables ThenBy . For example:

IOrderedQueryable<Application> ordered;

switch (filters.Sort)
{
    case "new":
        ordered = query.OrderByDescending(a => a.CreatedAt);
        break;
    case "old":
        ordered = query.OrderBy(a => a.CreatedAt);
        break;
    case "salary-asc":
        ordered = query.OrderBy(a => a.Profile.CompensationTypeRate.FromCompensation);
    default:
        // You need to work out what you want to do here. Maybe just
        // order by ID? You need to order by *something* to start with
        // in order to use ThenBy
}

// Apply the same secondary ordering, regardless of the primary one
ordered = ordered.ThenBy(x => x.Grade);

// You can then continue to use ordered, or assign the value back
// to query:
query = ordered;

Note that all of this will still be lazy. The ordering won't actually happen until you try to use the results.