Omer van Kloeten's .NET Zen

Linq: ContainsAtLeast and AggregationOrDefault

I've created a couple of useful extension methods that I like to use with Linq, so here they are:

ContainsAtLeast

I've noticed that there's no way to find out whether a collection has at least X items. The following takes the collection, tries to take X items from it and asks whether it succeeded or not:

public static bool ContainsAtLeast<T>(this IEnumerable<T> enumeration,
                                      int count)
{
    // Check to see that enumeration is not null
    if (enumeration == null)
        throw new ArgumentNullException("enumeration");

    return (from t in enumeration.Take(count)
            select t)
            .Count() == count;
}

AggregationOrDefault

When I need the first item in a collection, I love using First when I need an exception and FirstOrDefault when I don't. However, this doesn't exist for aggregations and if your collection is empty, Max, Min, etc. will throw an exception.

public static T AggregationOrDefault<T>(this IEnumerable<T> enumeration,
                                        Func<IEnumerable<T>, T> aggregationMethod)
{
    // Check to see that enumeration is not null
    if (enumeration == null)
        throw new ArgumentNullException("enumeration");

    // Check to see that aggregationMethod is not null
    if (aggregationMethod == null)
        throw new ArgumentNullException("aggregationMethod");

    if (!enumeration.ContainsAtLeast(1))
        return default(T);

    return aggregationMethod(enumeration);
}

What this does is take a collection and an aggregation method, checks whether there's at least one item and applies the method. This is very useful, because most aggregation methods that take only one parameter - the collection, are not generic, so that would mean, just like in Linq itself, creating a copy of this method for every numeric type (as an example, see Max<T> compared to Max).

How to use it? Simple:

myEnumeration.AggregationOrDefault(Enumerable.Max);

In this case, sending the Max method to AggregationOrDefault.