/// <summary>
/// This is used from ExpressionStdDev for evaluating avg.
/// </summary>
public ExpressionAvg (ExpressionElement E)
{
Elements.Add (E);
}
public ExpressionElementComparer(ExpressionElement E1, DataRow Row)
{
_value1 = E1.Result (Row);
_row = Row;
if (_value1 == null || _value1 == DBNull.Value)
return;
_t1 = _value1.GetType ();
_RT1 = E1.ResultType (Row);
}
public int CompareTo (ExpressionElement E2)
{
object value1 = _value1;
object value2 = E2.Result (_row);
if ((value1 == null || value1 == DBNull.Value) && (value2 == null || value2 == DBNull.Value))
return 0;
else if (value2 == null || value2 == DBNull.Value)
return 1;
else if (value1 == null || value1 == DBNull.Value)
return -1;
Type t2 = value2.GetType ();
Type RT2 = E2.ResultType (_row);
if (_t1 == typeof (string) || t2 == typeof (string))
{
// FIXME: If one of elements are string they both should be???
return String.Compare(value1.ToString(), value2.ToString(), !_row.Table.CaseSensitive);
}
if (_t1 != t2)
{
value2 = Convert.ChangeType (value2, Type.GetTypeCode (_t1));
}
if (value1 is IComparable)
return ((IComparable)value1).CompareTo(value2);
return (int) _t1.InvokeMember ("CompareTo", BindingFlags.Default |
BindingFlags.InvokeMethod, null,
value1,
new object [] {value2});
}
/// <summary>
/// static method for comparing two ExpressionElement. This is used in =, <, >, <>, <=, >= elements.
/// If elements are equal returns 0, if E1 is less that E2, return -1 else if E1 is greater 1
/// </summary>
protected static int Compare (ExpressionElement E1, ExpressionElement E2, DataRow Row)
{
ExpressionElementComparer comparer = new ExpressionElementComparer(E1, Row);
return comparer.CompareTo(E2);
}