Error: xxx is not an lvalue

[flourish]

Hi,

why does the following code not compile -- or how to declare a (usable)
property of an associative array field?

//////////////////////
class Test
{
  private int[int] _testMap;
  public int[int] testMap() {return _testMap;}
}


void main()
{
  Test test = new Test();
  test.testMap[0] = 1;
}
/////////////////

*** Error: test.testMap() is not an lvalue


Regards,
    flourish