InvalidInput and AgainstExpression

[patrickiel]

Hello,
I have two questions:

1. Why do these two methods exist, wouldn't one be enough?

const int age = 16;
Guard.Against.InvalidInput(age, nameof(age), i => i >= 18, "To young!");
Guard.Against.AgainstExpression(i => i >= 18, age, "To young!");            

2. If T is string I get the following error, is this intended?

const string name = "Joe";
Guard.Against.InvalidInput(name, nameof(name), i => i.StartsWith("S"), "The name does not start with 'S'"); //OK
Guard.Against.AgainstExpression(i => i.StartsWith("S"), name, "The name does not start with 'S'"); // ERROR

here is the screenshot: