How to declare a class instance as a constant in C#?

I need to implement this:

static class MyStaticClass
{
    public const TimeSpan theTime = new TimeSpan(13, 0, 0);
    public static bool IsTooLate(DateTime dt)
    {
        return dt.TimeOfDay >= theTime;
    }
}

theTime is a constant (seriously :-), like π is, in my case it'd be pointless to read it from settings, for example. And I'd like it to be initialized once and never changed.

But C# doesn't seem to allow a constant to be initialized by a function (which a constructor is). How to overcome this?

c# .net constants

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1 Answer

Constants have to be compile time constant, and the compiler can't evaluate your constructor at compile time. Use readonly and a static constructor.

static class MyStaticClass
{
  static MyStaticClass()
  {
     theTime = new TimeSpan(13, 0, 0);
  }

  public static readonly TimeSpan theTime;
  public static bool IsTooLate(DateTime dt)
  {
    return dt.TimeOfDay >= theTime;
  }
}

In general I prefer to initialise in the constructor rather than by direct assignment as you have control over the order of initialisation.

answered 2011-06-03T18:40:51.553

How to declare a class instance as a constant in C#?

1 Answer

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