Pass property itself to function as parameter in C#

Question

I am looking for a method to pass property itself to a function. Not value of property. Function doesn\'t know in advance which property will be used for sorting. Simplest w

Answer 1

You can pass a property accessor to the method.

List SortBy(List toSort, Func getProp)
{
    if (toSort != null && toSort.Count > 0) {
        return toSort
            .OrderBy(x => getProp(x))
            .ToList();
    }
    return null;
}

You would call it like this:

var result = SortBy(toSort, x => x.maxSpeed);

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But you could go one step further and write your own extension method.

public static class CollectionExtensions
{
    public static List OrderByAsListOrNull(
        this ICollection collection, Func keySelector)

        if (collection != null && collection.Count > 0) {
            return collection
                .OrderBy(x => keySelector(x))
                .ToList();
        }
        return null;
    }
}

Now you can sort like this

List sorted = toSort.OrderByAsListOrNull(x => x.maxSpeed);

but also

Person[] people = ...;
List sortedPeople = people.OrderByAsListOrNull(p => p.LastName);

Note that I declared the first parameter as ICollection because it must fulfill two conditions:

1. It must have a Count property
2. It must be an IEnumerable in order to be able to apply the LINQ method OrderBy.

List is an ICollection but also an array Person[] as many other collections.

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So far, I have shown how you can read a property. If the method needs to set a property, you need to pass it a setter delegate as well

void ReadAndWriteProperty(Func getProp, Action setProp)

Where T is the type of the property.