利用C#9.0新语法如何提升if语句美感

string? hello = "hello world";
hello = null;

// 旧的方式
if (!string.IsNullOrEmpty(hello))
{
 Console.WriteLine($"{hello} has {hello.Length} letters.");
}

// 新的方式
if (hello is { Length: >0 })
{
 Console.WriteLine($"{hello} has {hello.Length} letters.");
}

string?[]? greetings = new string[2];
greetings[0] = "Hello world";
greetings = null;

// 旧的方式
if (greetings != null && !string.IsNullOrEmpty(greetings[0]))
{
 Console.WriteLine($"{greetings[0]} has {greetings[0].Length} letters.");
}

// 新的方式
if (greetings?[0] is {Length: > 0} hi)
{
 Console.WriteLine($"{hi} has {hi.Length} letters.");
}

ConsoleKeyInfo userInput = Console.ReadKey();

// 旧的方式
if (userInput.KeyChar == 'Y' || userInput.KeyChar == 'y')
{
 Console.WriteLine("Do something.");
}

// 新的方式
if (userInput.KeyChar is 'Y' or 'y')
{
 Console.WriteLine("Do something.");
}