In C#, how do I keep certain method calls out of the codebase entirely?

Question

I'm trying to get rid of all DateTime.Now method calls and replace them with my own GetNow() method, which may sometimes return a fixed date for testing purposes.

How can I enforce that no one adds a DateTime.Now call in the future? Can I use NDepend or StyleCop to check this on my continuous integration server?

Answer 1

With NDepend it is very easy to write this rule:

// <Name>Forbid DateTime.Now, use xxx.GetNow() instead</Name>
WARN IF Count > 0 IN 
SELECT METHODS WHERE 
IsDirectlyUsing "OPTIONAL:System.DateTime.get_Now()"

Notice:

• The prefix WARN IF Count > 0 IN that transforms the CQL query into a rule
• The way the property is referenced through the string System.DateTime.get_Now()
• The prefix OPTIONAL that means "Don't emit a compilation error if the property get_Now is not found". This makes sense since if your code doesn't use anymore get_Now(), it is not anymore referenced from NDepend analysis.

Also, to generate the original query...

SELECT METHODS WHERE 
IsDirectlyUsing "OPTIONAL:System.DateTime.get_Now()"

...just right-click DateTime.get_Now() and choose Select methods ... that are directly using me

Answer 2

Firstly, DateTime.Now is a property.
That means you don't need to put parenthesis after call.

Secondly, if by testing purposes you mean a framework like NUnit, you might want to check out Microsoft Moles which allows you to substitute any static method call with your own custom implementation while testing. Heck, it's cool:

[Test]
[ExpectedException (typeof (Y2KBugException))]
public void TestY2KBug ()
{
    MDateTime.NowGet = () => new DateTime (2001, 1, 1);
    Bomb.DetonateIfY2K ();
}


public static class Bomb {
    public static void DetonateIfY2K ()
    {
        if (DateTime.Now == new DateTime (2001, 1, 1))
            throw new Y2KBugException (); // take cover!
    }
}