mcs/class/System.Data/Mono.Data.SqlExpressions/Comparison.cs

   1 //
   2 // Comparison.cs
   3 //
   4 // Author:
   5 //   Juraj Skripsky (juraj@hotfeet.ch)
   6 //
   7 // (C) 2004 HotFeet GmbH (http://www.hotfeet.ch)
   8 //
   9
  10 using System;
  11 using System.Data;
  12
  13 namespace Mono.Data.SqlExpressions {
  14         public class Comparison : BinaryOpExpression {
  15                 public Comparison (Operation op, IExpression e1, IExpression e2) : base (op, e1, e2) {}
  16
  17                 override public object Eval (DataRow row)
  18                 {
  19                         IComparable o1 = (IComparable)expr1.Eval (row);
  20                         IComparable o2 = (IComparable)expr2.Eval (row);
  21
  22                         if (o1 == null || o2 == null) {
  23                                 if (o1 == null && o2 == null)
  24                                         return (op == Operation.EQ);
  25                                 else
  26                                         return (op == Operation.NE);
  27                         }
  28
  29                         switch(Compare (o1, o2, row.Table.CaseSensitive)) {
  30                         case -1:
  31                                 return (op == Operation.NE || op == Operation.LE || op == Operation.LT);
  32                         case 0:
  33                         default:
  34                                 return (op == Operation.EQ || op == Operation.LE || op == Operation.GE);
  35                         case 1:
  36                                 return (op == Operation.NE || op == Operation.GE || op == Operation.GT);
  37                         }
  38                 }
  39
  40                 internal static int Compare (IComparable o1, IComparable o2, bool caseSensitive)
  41                 {
  42                         //TODO: turn this "conversion pipeline" into something nicer
  43
  44                         try {
  45                                 if (o1 is string && Numeric.IsNumeric (o2))
  46                                                 o1 = (IComparable)Convert.ChangeType (o1, o2.GetType ());
  47                                 if (o2 is string && Numeric.IsNumeric (o1))
  48                                                 o2 = (IComparable)Convert.ChangeType (o2, o1.GetType ());
  49                         } catch (FormatException) {
  50                                 throw new EvaluateException (String.Format ("Cannot perform compare operation on {0} and {1}.", o1.GetType(), o2.GetType()));
  51                         }
  52
  53                         if (o1 is string && o2 is string && !caseSensitive) {
  54                                 o1 = ((string)o1).ToLower();
  55                                 o2 = ((string)o2).ToLower();
  56                         }
  57
  58                         if (o1.GetType () != o2.GetType ())
  59                                 o2 = (IComparable)Convert.ChangeType (o2, o1.GetType ());
  60
  61                         return o1.CompareTo (o2);
  62                 }
  63         }
  64 }