CODEWITHSUNDEEP
c#linq
user3953989
user3953989

Reputation: 1951

Linq OrderBy with an expression variable

I'm trying to figure out how to sort by a variable, not a string. I believe I should be able to represent x => x.SomeProperty and save that to a variable and pass it into the OrderBy method but can't figure out what to use here.

SomeType sortExpr = null;
switch(sortByColumnName)
{
    case "Name":
        sortExpr = x => x.Name
        break;
    case "Age":
        sortExpr = x => x.Age
        break;
    case "OtherThing":
        sortExpr = x => x.OtherReference.Name
        break;
}

if (sortDirection == "asc")
    query = query.OrderBy(sortExpr);
else
    query = query.OrderByDescending(sortExpr);

Upvotes: 1

Views: 1476

Answers (1)

Michał Turczyn
Michał Turczyn

Reputation: 37500

As already said, OrderBy accepts Func<TSource,TKey> keySelector as its argument so sortExpr should e of that type, where TSource is object, which is stored in collection you want to sort, let's say of User class. TKey is type of property you want to sort by, since this can be of arbitrary type, you can make it object, as this type parameter is covariant.

So declare like

Func<User, object> sortExpr;

and rest code can stay as it is.

EDIT

If you are using IQueryable<TSource>.OrderBy version, which requires Expression<Func<TSource, TKey>>, then you just need to delare the variable as:

Expression<Func<User, object>> sortExpr;

Upvotes: 4

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