Question

I would like to try this code:

public struct Direction
{
   private int _azimuth;

   public int Azimuth
   {
     get { return _azimuth; }
     set { _azimuth = value; }
   }       

   public Direction(int azimuth)
   { 
      Azimuth = azimuth
   } 
}

But it fails on compilation, I understand that struct need to init all its fields.
but i am trying to understand what happens under the CLR\IL hoods.
why it need all the fields before any other method\property\this etc.

Thanks.

Answer 1

Value Types are created on the stack (unless nested within a reference type) There is something about fields/locations on the stack that the CLR can’t guarantee that they will be zeroed out (contrary to fields/locations on the managed heap which are guaranteed to be zeroed out). Hence they must be written to before being read. Otherwise it’s a security hole.

The struct’s default ctor (which takes no parameters and which you’re not allowed to explicitly specify) zeroes out all fields of a struct and hence you can use a struct after you do.

new BimonthlyPairStruct()

However when you implement your parameterized ctor, you must ensure that all fields have been initialized – which is required for the CLR to pass your code as safe/verified .

See Also: CLR via C# 2nd Ed – Pg 188