How it works
Any answers whether at least one element matches, while All answers whether every element matches. Both can stop as soon as the answer is known. In this input there is a negative value, and the values are not all positive. All returns true for an empty sequence because there is no counterexample; that mathematical behavior may differ from a business rule requiring at least one item.
Combine Any with All when both presence and universal validity are required. Prefer an existence operation to counting every match when the consumer only needs a yes or no answer.
Create an empty order array and express the rule “at least one order and every total is positive.” Compare the combined expression with All by itself.
A working example
using System;
using System.Linq;
using System.Collections.Generic;
using System.Globalization;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
var values = new[] { 3, -1, 5 };
Console.WriteLine(values.Any(x => x < 0));
Console.WriteLine(values.All(x => x > 0));
Console.WriteLine(Array.Empty<int>().All(x => x > 0));
Expected output
True False True
Try this
An empty collection passes All unless your rule checks presence too.
An empty collection passes All unless your rule checks presence too.