All

Returns true if the provided predicate function returns true for all elements in a collection, false otherwise.

• Use IEnumerable.ToArray(), Array.TrueForAll() to test if all elements in the collection return true based on the predicate function, match.
• Omit the predicate function, match, to use the overload that checks if each value is different from null by default.

using System.Collections.Generic;
using System.Linq;

public static partial class _30s
{
  public static bool All<T>(IEnumerable<T> data, Predicate<T> match)
  {
    return Array.TrueForAll(data.ToArray(), match);
  }
  public static bool All<T>(IEnumerable<T> data)
  {
    return Array.TrueForAll(data.ToArray(), val => val != null);
  }
}

int[] nums = { 4, 2, 3 };

_30s.All(nums, x => x > 1); // true
_30s.All(nums); // true