Why cannot I use String.Contains() if default string is null?

Question

From MSDN doc:

public bool Contains(
    string value
)

Return Value: true if the value parameter occurs within this string, or if value is the empty string (""); otherwise, false.

Exception: ArgumentNullException: value is null.

Example:

string s = string.Empty; //or string s = "";
Console.WriteLine(s.Contains("Hello World!")); //output: False

If I change it to:

try
{
   string s = null; //or string s;
   Console.WriteLine(s.Contains("Hello World!"));
}
catch (Exception e)
{
   Console.WriteLine(e.Message);
}

It'll throw an error message: Object reference not set to an instance of an object since string doesn't have a default value (like "") from Default Values Table (C# Reference),

Please come back to the example, the code will work if I declare s:

string s = "";

Now, Object s is set to an instance of an object.

So, my question is: Does MSDN forgot something like: s cannot be null?

To check it, I've tried:

string s = null;
Console.WriteLine(!string.IsNullOrEmpty(s) ? s.Contains("Hello World!") : false);

It should work.

Answer 1

the new compilier allows you to do it with the condition check simplified.

string s = null;
Console.WriteLine(s?.Contains("Hello World!"));