Is it possible to use LINQ to check if all numbers in a list are increasing monotonically?

Question

I\'m interested if there is a way, in LINQ, to check if all numbers in a list are increasing monotonically?

Example

List l         


        

Answer 1

If you want to check whether a list always is increasing from index to index:

IEnumerable<int> list = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 10 };
bool allIncreasing = !list
    .Where((i, index) => index > 0 && list.ElementAt(index - 1) >= i)
    .Any();

Demo

But in my opinion a simple loop would be more readable in this case.

Answer 2

Consider an implementation like the following, which enumerates the given IEnumerable only once. Enumerating can have side-effects, and callers typically expect a single pass-through if that's possible.

public static bool IsIncreasingMonotonically<T>(
    this IEnumerable<T> _this)
    where T : IComparable<T>
{
    using (var e = _this.GetEnumerator())
    {
        if (!e.MoveNext())
            return true;
        T prev = e.Current;
        while (e.MoveNext())
        {
            if (prev.CompareTo(e.Current) > 0)
                return false;
            prev = e.Current;
        }
        return true;
    }
}