Is there a bug in TimeSpan?

Question

This will output "0":

TimeSpan span = TimeSpan.Zero;
span.Add(TimeSpan.FromMinutes(5));
Console.WriteLine(span.TotalSeconds);   -----> 

However, this will output "300":

TimeSpan span = TimeSpan.Zero.Add(TimeSpan.FromMinutes(5));
Console.WriteLine(span.TotalSeconds);   -----> 

Is this a known bug?

Answer 1

TimeSpan.Add does not modify the input - it returns a new TimeSpan which is the input plus the addend:

Remarks

The return value must be between TimeSpan.MinValue and TimeSpan.MaxValue; otherwise, an exception is thrown.

The return value is a new TimeSpan; the original TimeSpan is not modified.