private SqlExpression EvalDateTimeValue(NPathDateTimeValue value)
		{
			SqlDateTimeLiteral dateTimeLiteral = new SqlDateTimeLiteral(value.Value) ;
			return dateTimeLiteral;
//			string paramName = GetParameterName();
//			IQueryParameter param = new QueryParameter(paramName, DbType.DateTime, value.Value ) ;
//			ResultParameters.Add(param);
//			SqlParameter sqlParam = select.AddSqlParameter(paramName, DbType.DateTime, value.Value) ;
//			return sqlParam ;
		}
 protected virtual void EmitDateTimeValue(NPathDateTimeValue value)
 {
     Write("'");
     Write(value.Value);
     Write("'");
 }
        private IValue ParseValue()
        {
            IValue operand = null;

            bool isNegative = false;
            if (tokenizer.GetCurrentToken().IsType("sign"))
            {
                if (tokenizer.GetCurrentToken().IsType("minus"))
                    isNegative = true;

                tokenizer.MoveNext();
            }

            Token currentToken = tokenizer.GetCurrentToken();

            #region parse value

            if (currentToken.IsType("null"))
            {
                NPathNullValue nullOperand = new NPathNullValue();
                operand = nullOperand;
                tokenizer.MoveNext();
            }
            else if (currentToken.IsType("parameter"))
            {
                NPathParameter parameterOperand = new NPathParameter();
                parameterOperand.Value = parameterQueue[0];
                parameterQueue.RemoveAt(0);
                operand = parameterOperand;
                tokenizer.MoveNext();
            }
            else if (tokenizer.GetCurrentToken().IsType("textsearch"))
            {
                return ParseSearchFunctionExpression();
            }
            else if (currentToken.IsType("function") && IsInSelectClause() || currentToken.IsType("isnull") || currentToken.IsType("soundex"))
            {
                NPathFunction functionOperand = new NPathFunction();

                if (currentToken.IsType("soundex"))
                    functionOperand = new NPathSoundexStatement();
                if (currentToken.IsType("sum"))
                    functionOperand = new NPathSumStatement();
                if (currentToken.IsType("isnull"))
                    functionOperand = new NPathIsNullStatement();
                if (currentToken.IsType("count"))
                    functionOperand = new NPathCountStatement();
                if (currentToken.IsType("avg"))
                    functionOperand = new NPathAvgStatement();
                if (currentToken.IsType("min"))
                    functionOperand = new NPathMinStatement();
                if (currentToken.IsType("max"))
                    functionOperand = new NPathMaxStatement();

                tokenizer.MoveNext();
                tokenizer.GetCurrentToken("(", "(");
                tokenizer.MoveNext();
                if (tokenizer.GetCurrentToken().IsType("distinct"))
                {
                    functionOperand.Distinct = true;
                    tokenizer.MoveNext();
                }

                functionOperand.Expression = ParseBooleanExpression();
                tokenizer.GetCurrentToken(")", ")");
                tokenizer.MoveNext();

                operand = functionOperand;
            }
            else if (currentToken.IsType("date"))
            {
                NPathDateTimeValue dateOperand = new NPathDateTimeValue();
                dateOperand.Value = DateTime.Parse(currentToken.Text);
                operand = dateOperand;
                tokenizer.MoveNext();
            }
            else if (currentToken.IsType("decimal"))
            {
                NPathDecimalValue decimalOperand = new NPathDecimalValue();
                decimalOperand.Value = double.Parse(currentToken.Text, NumberFormatInfo.InvariantInfo);
                decimalOperand.IsNegative = isNegative;
                operand = decimalOperand;
                tokenizer.MoveNext();
            }
            else if (currentToken.IsType("string"))
            {
                NPathStringValue stringOperand = new NPathStringValue();
                string text = currentToken.Text;
                text = text.Substring(1, text.Length - 2);

                if (currentToken.IsType("string '")) // do not localize
                    text = text.Replace("''", "'");
                else if (currentToken.IsType("string \""))
                    text = text.Replace("\"\"", "\""); // do not localize

                stringOperand.Value = text;
                operand = stringOperand;
                tokenizer.MoveNext();
            }
            else if (currentToken.IsType("boolean"))
            {
                NPathBooleanValue booleanOperand = new NPathBooleanValue();
                booleanOperand.Value = bool.Parse(currentToken.Text);
                operand = booleanOperand;
                tokenizer.MoveNext();
            }
            else if (currentToken.IsType("guid"))
            {
                NPathGuidValue guidOperand = new NPathGuidValue();
                guidOperand.Value = currentToken.Text;
                operand = guidOperand;
                tokenizer.MoveNext();
            }
            else if (currentToken.IsType("property path")) // do not localize
            {
                if (tokenizer.GetNextToken().IsType("("))
                {
                    string fullPath = currentToken.Text;
                    string propertyPath = "";
                    string methodName = "";
                    int lastIndexOfDot = fullPath.LastIndexOf(".");
                    if (lastIndexOfDot > 0)
                    {
                        propertyPath = fullPath.Substring(0, lastIndexOfDot);
                        methodName = fullPath.Substring(lastIndexOfDot + 1);
                    }
                    else
                    {
                        methodName = fullPath;
                    }

                    NPathMethodCall call = new NPathMethodCall();
                    call.MethodName = methodName;

                    call.PropertyPath = new NPathIdentifier();
                    call.PropertyPath.Path = propertyPath;
                    call.PropertyPath.IsNegative = isNegative;

                    //TODO:add method support here
                    tokenizer.MoveNext(); //move past "("
                    tokenizer.MoveNext();
                    while (!tokenizer.GetCurrentToken().IsType(")"))
                    {
                        IValue param = ParseExpression();
                        call.Parameters.Add(param);
                        if (tokenizer.GetCurrentToken().IsType("comma"))
                        {
                            tokenizer.MoveNext();
                        }
                        else
                        {
                            tokenizer.GetCurrentToken(")", ")");
                        }

                    }
                    tokenizer.MoveNext();
                    operand = call;
                }
                else if (tokenizer.GetNextToken().IsType("["))
                {
                    CurrentPropertyPrefix = currentToken.Text + ".";
                    NPathBracketGroup bracketGroup = new NPathBracketGroup();
                    tokenizer.MoveNext();
                    ParseBracketGroup(bracketGroup);
                    CurrentPropertyPrefix = "";
                    NPathParenthesisGroup parens = new NPathParenthesisGroup();
                    parens.Expression = bracketGroup.Expression;
                    operand = parens;
                }
                else
                {
                    NPathIdentifier propertyOperand = new NPathIdentifier();
                    propertyOperand.Path = CurrentPropertyPrefix + currentToken.Text;

                    propertyOperand.ReferenceLocation = IsInSelectClause() ? NPathPropertyPathReferenceLocation.SelectClause : NPathPropertyPathReferenceLocation.WhereClause;

                    //CurrentQuery.AddPropertyPathReference(propertyOperand.Path) ;

                    propertyOperand.IsNegative = isNegative;
                    operand = propertyOperand;
                    tokenizer.MoveNext();
                }
            }
            else if (currentToken.IsType("("))
            {
                NPathParenthesisGroup parenthesisOperand = new NPathParenthesisGroup();
                ParseParenthesisGroup(parenthesisOperand);
                parenthesisOperand.IsNegative = isNegative;
                operand = parenthesisOperand;
            }
            else
            {
                //unknown value?
                throw GetUnknownTokenException();
            }

            #endregion

            return operand;
        }