Getting the difference of two DateTime instances in milliseconds

Question

What would be a proper fool-proof way of doing so? I am using ASP.NET MVC 3.

Solution 1

        DateTime a = ...
        DateTime b = ...
        var ms = a.Subtract(b).TotalMilliseconds;

Solution 2

(datetime2 - datetime1).TotalMilliseconds

Solution 3

I'm thinking this should work. Since you asked for foolproof, I'm assuming you don't know which of the two is the later date :)

Math.Abs((date1 - date2).TotalMilliseconds)