C#

struct Foo
{
  int a;
  int b;

  public readonly static Empty;

  static Foo() { Empty = new Foo() ;} //mite not even be neccesary infact, 
                                      //should be initialized to default value
}

...

Foo[] a = new Foo[2];
for (int i = 0; i < a.Length; i++)
{
  if (a[0].Equals(Foo.Empty)) // does a field by field comparision in valuetype
  {
     Console.WriteLine("a[{0}] = Foo.Empty", i);
  }
}

struct Foo
{
  bool init;
  int a;
  int b;

  public int A
  {
    get {return a;} set { init = true; a= value;}
  }
  public int B
  {
    get {return b;} set { init = true; b= value;}
  }
  
  ... the rest of previous example.
}

string sql = "SELECT ... WHERE DateField < @Date";
SqlCommand cmd = new SqlCommand(sql, conn);
cmd.Parameters.Add("@Date", mydate);
SqlDataReader rdr = cmd.ExectueReader()
while(rdr.Read())
{
    // This cycle will repeat for every row returned. If you get two
    // rows, process one row here, get to the end of the while loop, and
    // when rdr.Read() is called again, you'll get the second record.
}