最初に数字が出たところから末尾までの文字列を返す

test1.cs

        [Test]
        public void _最初に数字が出たところから末尾までの文字列を返す() {
            var needle = Enumerable.Range(0, 10).Select(c => (char)('0' + c)).ToArray();

            var text1 = "qazxdftyujh6olkmnbgfds";
            var i1 = text1.IndexOfAny(needle);
            var actual1 = i1 >= 0 ? text1.Substring(i1) : "";
            Assert.That(actual1, Is.EqualTo("6olkmnbgfds"));

            var text2 = "qsxcvhikol,kmjbgvf";
            var i2 = text2.IndexOfAny(needle);
            var actual2 = i2 >= 0 ? text2.Substring(i2) : "";
            Assert.That(actual2, Is.Empty);
        }

test2.cs

        [Test]
        public void _最初に数字が出たところから末尾までの文字列を返す_Linq馬鹿の場合() {
            var needle = new HashSet<char>(Enumerable.Range(0, 10).Select(c => (char)('0' + c)));

            var text1 = "qazxdftyujh6olkmnbgfds";
            var actual1 = string.Join("", text1.Cast<char>().SkipWhile(c => !needle.Contains(c)));
            Assert.That(actual1, Is.EqualTo("6olkmnbgfds"));

            var text2 = "qsxcvhikol,kmjbgvf";
            var actual2 = string.Join("", text2.Cast<char>().SkipWhile(c => !needle.Contains(c)));
            Assert.That(actual2, Is.Empty);
        }