System.Data.LikeNode.Eval C# (CSharp) Méthode

        internal override object Eval(DataRow row, DataRowVersion version)
        {
            object vRight;
            object vLeft = _left.Eval(row, version);
            string substring;


            if ((vLeft == DBNull.Value) || (_left.IsSqlColumn && DataStorage.IsObjectSqlNull(vLeft)))
                return DBNull.Value;

            if (_pattern == null)
            {
                vRight = _right.Eval(row, version);

                if (!(vRight is string) && !(vRight is SqlString))
                {
                    SetTypeMismatchError(_op, vLeft.GetType(), vRight.GetType());
                }

                if (vRight == DBNull.Value || DataStorage.IsObjectSqlNull(vRight))
                    return DBNull.Value;
                string rightStr = (string)SqlConvert.ChangeType2(vRight, StorageType.String, typeof(string), FormatProvider);


                // need to convert like pattern to a string

                // Parce the original pattern, and get the constant part of it..
                substring = AnalyzePattern(rightStr);

                if (_right.IsConstant())
                    _pattern = substring;
            }
            else
            {
                substring = _pattern;
            }

            if (!(vLeft is string) && !(vLeft is SqlString))
            {
                SetTypeMismatchError(_op, vLeft.GetType(), typeof(string));
            }

            // WhiteSpace Chars Include : 0x9, 0xA, 0xB, 0xC, 0xD, 0x20, 0xA0, 0x2000, 0x2001, 0x2002, 0x2003, 0x2004, 0x2005, 0x2006, 0x2007, 0x2008, 0x2009, 0x200A, 0x200B, 0x3000, and 0xFEFF.
            char[] trimChars = new char[2] { (char)0x20, (char)0x3000 };
            string tempStr;
            if (vLeft is SqlString)
                tempStr = ((SqlString)vLeft).Value;
            else
                tempStr = (string)vLeft;

            string s1 = (tempStr).TrimEnd(trimChars);

            switch (_kind)
            {
                case match_all:
                    return true;
                case match_exact:
                    return (0 == table.Compare(s1, substring));
                case match_middle:
                    return (0 <= table.IndexOf(s1, substring));
                case match_left:
                    return (0 == table.IndexOf(s1, substring));
                case match_right:
                    string s2 = substring.TrimEnd(trimChars);
                    return table.IsSuffix(s1, s2);
                default:
                    Debug.Assert(false, "Unexpected LIKE kind");
                    return DBNull.Value;
            }
        }