| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| using System; |
| using System.Text; |
| |
| namespace Apache.NMS.Selector |
| { |
| /// <summary> |
| /// A boolean expression which checks if an expression value is null. |
| /// </summary> |
| public class IsNullExpression : BooleanUnaryExpression |
| { |
| private bool notNot; |
| |
| protected override string ExpressionSymbol |
| { |
| get { return notNot ? "IS NULL" : "IS NOT NULL"; } |
| } |
| |
| public IsNullExpression(IExpression right, bool notNot) |
| : base(right) |
| { |
| this.notNot = notNot; |
| } |
| |
| public override object Evaluate(MessageEvaluationContext message) |
| { |
| object rvalue = Right.Evaluate(message); |
| |
| bool answer = (rvalue == null || rvalue == ConstantExpression.NULL); |
| |
| return notNot ? answer : !answer; |
| } |
| |
| public override string ToString() |
| { |
| StringBuilder answer = new StringBuilder(); |
| answer.Append(Right); |
| answer.Append(" "); |
| answer.Append(ExpressionSymbol); |
| return answer.ToString(); |
| } |
| } |
| } |