How declare values in C#

function Start()
{
// Store a bunch of different positions in an Array:
var aPositions : Array = [new Vector3(0,0,0),
new Vector3(1,2,1),
new Vector3(2,1,1),
new Vector3(2,0,0),
new Vector3(0,3,0)];

 var rot : Quaternion = Quaternion.identity;

 // Loop as many times as there are elements in the aPositions Array:
 for(i=0; i<aPositions.length; i++)
 {
      Instantiate(myCube, aPositions*, rot); // Put a new cube on the screen using the i'th position* 

}
}

C# syntax is

Quaternion rot = Quaternion.identity;
int i = 5;

etc.

To use an array, look at the C# documentation