the origional post is here: http://weblogs.asp.net/bleroy/archive/2004/08/03/Don_2700_t-redirect-after-setting-a-Session-variable-_2800_or-do-it-right_2900_.aspx

 Polymorphism, Method Hiding and Overriding in C#

 Overview

One of the fundamental concepts of object oriented software development is polymorphism. The term polymorphism (from the Greek meaning "having multiple forms") in OO is the characteristic of being able to assign a different meaning or usage to something in different contexts - specifically, to allow a variable to refer to more than one type of object.

Example Class Hierarchy

Let's assume the following simple class hierarchy with classes A, B and C for the discussions in this text. A is the super- or base class, B is derived from A and C is derived from class B. In some of the easier examples, we will only refer to a part of this class hierarchy.

Inherited Methods

A method Foo() which is declared in the base class A and not redeclared in classes B or C is inherited in the two subclasses

    using System;
    namespace Polymorphism
    {
        class A
        {
            public void Foo() { Console.WriteLine("A::Foo()"); }
        }

        class B : A {}

        class Test
        {
            static void Main(string[] args)
            {
                A a = new A();
                a.Foo();  // output --> "A::Foo()"

                B b = new B();
                b.Foo();  // output --> "A::Foo()"
            }
        }
    }
     

The method Foo() can be overridden in classes B and C:

    using System;
    namespace Polymorphism
    {
        class A
        {
              public void Foo() { Console.WriteLine("A::Foo()"); }
        }

        class B : A
        {
              public void Foo() { Console.WriteLine("B::Foo()"); }
        }

        class Test
        {
            static void Main(string[] args)
            {
                A a;
                B b;

                a = new A();
                b = new B();
                a.Foo();  // output --> "A::Foo()"
                b.Foo();  // output --> "B::Foo()"

                a = new B();
                a.Foo();  // output --> "A::Foo()"
            }
        }
    }
     

There are two problems with this code.

The output is not really what we, say from Java, expected. The method Foo() is a non-virtual method. C# requires the use of the keyword virtual in order for a method to actually be virtual. An example using virtual methods and polymorphism will be given in the next section.

Although the code compiles and runs, the compiler produces a warning: ...\polymorphism.cs(11,15): warning CS0108: The keyword new is required on 'Polymorphism.B.Foo()' because it hides inherited member 'Polymorphism.A.Foo()'

This issue will be discussed in section Hiding and Overriding Methods.

Virtual and Overridden Methods

Only if a method is declared virtual, derived classes can override this method if they are explicitly declared to override the virtual base class method with the override keyword.

    using System;
    namespace Polymorphism
    {
        class A
        {
            public virtual void Foo() { Console.WriteLine("A::Foo()"); }
        }

        class B : A
        {
            public override void Foo() { Console.WriteLine("B::Foo()"); }
        }

        class Test
        {
            static void Main(string[] args)
            {
                A a;
                B b;

                a = new A();
                b = new B();
                a.Foo();  // output --> "A::Foo()"
                b.Foo();  // output --> "B::Foo()"

                a = new B();
                a.Foo();  // output --> "B::Foo()"
            }
        }
     }

Method Hiding

Why did the compiler in the second listing generate a warning? Because C# not only supports method overriding, but also method hiding. Simply put, if a method is not overriding the derived method, it is hiding it. A hiding method has to be declared using the new keyword. The correct class definition in the second listing is thus:

    using System;
    namespace Polymorphism
    {
        class A
        {
            public void Foo() { Console.WriteLine("A::Foo()"); }
        }

        class B : A
        {
            public new void Foo() { Console.WriteLine("B::Foo()"); }
        }

        class Test
        {
            static void Main(string[] args)
            {
                A a;
                B b;

                a = new A();
                b = new B();
                a.Foo();  // output --> "A::Foo()"
                b.Foo();  // output --> "B::Foo()"

                a = new B();
                a.Foo();  // output --> "A::Foo()"
            }
        }
    }

Combining Method Overriding and Hiding

Methods of a derived class can both be virtual and at the same time hide the derived method. In order to declare such a method, both keywords virtual and new have to be used in the method declaration:

            class A
            {
                public void Foo() {}
            }

            class B : A
            {
                public virtual new void Foo() {}
            }
     

A class C can now declare a method Foo() that either overrides or hides Foo() from class B:

            class C : B
            {
                public override void Foo() {}
                // or
                public new void Foo() {}
            }

Conclusion

• C# is not Java.
• Only methods in base classes need not override or hide derived methods. All methods in derived classes require to be either defined as new or as override.
• Know what your doing and look out for compiler warnings.

早上醒来发现短信，MSN，QQ上都是朋友的祝福，很是感动

回到杭州就是感觉不一样。

 

25岁是一个里程碑。是承上启下的节点。

到了25岁就不能再孩子气，

到了25岁就不能再装做自己是不谙世事刚从学校出来的大学生

到了25岁就要开始承担更多的责任

到了25岁就要开始对当初的梦想做更实际的行动

 

同时，这个年纪也反应了我现在的生活状态和社会阶层。比下有余，比上不足

早就下决心要好好闯荡一番

而从今天起，要迈出真正的第一步

 

已经不再迷茫

已经决定不再漂泊

已经锁定未来发展目标

 

世上有可以挽回的和不可挽回的事，而时间经过就是一种不可挽回的事

就以同月同日生的村上春树的话段来纪念这逝去的25年吧

首先我想说北京彻底把我冰冻了，从身体到大脑。刚好,让我能够冷静下来，对这个多灾多难，跌宕起伏的366天做个小小总结。

08年去过的城市；坐过十六个航班,到访过杭州, 北京, 上海, 香港, Brisbane, Macky, Sydney 和 Canberra。遗憾的是因为金融危机东瀛之旅最终无限延期

08年做过的大事；悉尼反媒体不公正报道大游行，堪培拉保卫圣火运动，经历了整个SWIFT和MAC项目

08年的学业； 研究生课程稳步前进，通过微软认证技术专家MCTS WSS3.0 Con和MCTS MOSS 2007 Con

08年的事业；第一次升职，第一次出差，第一次常驻客户，第一次体验身边同事被裁员

08年的健康；从2月份身体彻底罢工到开始进行全面医治+运动，现在基本回到正轨

08年的改变：不再通宵，开始吃早饭，注意运动，开车上下班，定期去健身房，游泳，开始打网球

08年的感慨：自然的力量，西方的偏见，国人素质的参差不齐，国货质量的悲哀，澳洲移民局的无能，身边朋友开始有小孩，中国要强大

08年的个人问题；继续单身

------------------------------------------------------------------------------------------------------------

09年的八大目标

1. 实现单人日本之旅

2. 在2009年拿到MASTER学位

3. 保持身体健康

4. Canon 5D MKII

5. 继续提升网球技能

6. 考出MCPD WEB DEVELOPER

7. 工作上能比今年多出3成业绩

8. 学会蝶泳

发现工作以后就没有怎么好好静下心来读过一整本书 开始喜欢几百字的评论文章 没有时间去细细品味新的音乐 只是在开车的时候让IPOD胡乱SHUFFLE 甚至一部电影，要是有给我PAUSE的机会 大凡都会分好几次看完 是浮躁还是工作读书后的心疲力竭？ 或是物质生活压力症在蚕食我的精神世界？ 需要精神上的COOL DOWN 整理我想要的 我想成为的 我想面对的 时间越来越少 不再像大学里那样自由支配 一些不必要的爱好需要退化~ 一些不必要的娱乐需要缩减~ 也许经济危机来的正是时候，让我手头的资产贬值 警示我冒进的危险 提供我反思的空间 我呢，还在自己的世界慢慢爬行 会因为和朋友谈论公司的事情而踌躇满志 会因为在UNI里拿到一个HD的ASSIGNMENT而继续骗自己学术重要性 会因为写出一个优化的SQL QUERY而妄想自己是疯狂IT科学家 也会因为看一部单纯的海角七号而动摇自己画上红叉叉的爱情论 果然每个人都有自己的生命轨迹 COPY是不会成功的 唯有不断地自我修正了 晚上很凉，完全没有换季的感觉 澳洲的夏日没有知了叫 只有热热的海风

项目里用到了，觉得有必要记下来，不然琢磨了半天的成果又忘记了，控件用的是RAD TREE VIEW，理论都是相通的

CS端代码：首先是递归函数主体，先查找子目录，加为节点，再查找每个子目录下的文件，加为节点

 protected void BuildDirectoryTree(RadTreeNode parentNode)
        {
            // Handle Directories
            var directories = Directory.GetDirectories(parentNode.Value).Select(d => new RadTreeNode() { Text = d.Substring(d.LastIndexOf("\\")+1), Value = d });

            foreach (var directory in directories)
            {
                BuildDirectoryTree(directory);
                parentNode.Nodes.Add(directory);
            }

            // Handle Files
            var files = Directory.GetFiles(parentNode.Value).Select(f => new RadTreeNode() { Text = f.Substring(f.LastIndexOf("\\") + 1), Value = f });
            parentNode.Nodes.AddRange(files);          
        }

然后是调用，我直接拿项目里的做例子了：

protected void lbtnAddTemplate_Click(object sender, EventArgs e)
        {
            string quoteNo = Request.QueryString["QuoteNo"];
            HyperLink hlTemplateQuoteFolder = (HyperLink)quoteView.FindControl("hlTemplateQuoteFolder");
            RadTreeView rtvTemplateFilesList = (RadTreeView)quoteView.FindControl("rtvTemplateFilesList");

            if (!string.IsNullOrEmpty(quoteNo))
            {
                if (Directory.Exists(strTemplatePath))
                {
                    RadTreeNode rootNode = new RadTreeNode { Text = "Templates", Value = strTemplatePath };
                    BuildDirectoryTree(rootNode);

                    rtvTemplateFilesList.Nodes.Add(rootNode);
                }
            }

        }

TREE VIEW看起来像这样，然后当用户选中了他们要的文件后，选择添加会把这些文件拷到特定目录下（维持现在的位置）

protected void btnAddNewTemplate_Click(object sender, EventArgs e)
        {
            string message = string.Empty;
           
            RadTreeView rtvTemplateFilesList = (RadTreeView)quoteView.FindControl("rtvTemplateFilesList");
            IList<RadTreeNode> fileLst = rtvTemplateFilesList.CheckedNodes;

            // Create a QuoteNo folder
            if (!string.IsNullOrEmpty(QuoteNo))
            {
                string quotePath = Path.Combine(quoteRootPath, QuoteNo);
                // Check if the directory exists, if not then create it

                if (!Directory.Exists(quotePath))
                {
                    Directory.CreateDirectory(quotePath);
                }

                // Go through the list and copy all the files
                foreach (var item in fileLst)
                {
                    if (File.Exists(item.Value))
                    {
                        string relativeFolder = item.Value.Remove(item.Value.LastIndexOf("\\"));
                        if (relativeFolder.LastIndexOf("\\") < relativeFolder.Length - 1)
                        {
                            relativeFolder += "\\";
                        }
                        relativeFolder = relativeFolder.Replace(strTemplatePath, "");
                        string destinationFolder = Path.Combine(quotePath, relativeFolder);

                        if (!Directory.Exists(destinationFolder))
                        {
                            Directory.CreateDirectory(destinationFolder);
                        }
                        File.Copy(item.Value, Path.Combine(destinationFolder, item.Text),true);
                    }
                }
            }

            //hide the panel
            System.Diagnostics.Process.Start(@"c:\");
            AjaxControlToolkit.ModalPopupExtender mpAddNewTemplate = (AjaxControlToolkit.ModalPopupExtender)quoteView.FindControl("mpAddNewTemplate");
            mpAddNewTemplate.Hide();
               
            Response.Redirect("QuoteDetails.aspx?QuoteNo=" + QuoteNo);
        }

如果想把整个FOLDER包括里面所有东西拷贝到另一个地方的话，有一个METHOD更简单：

  protected void copyDirectory(string Src, string Dst)
        {
            // Copy directory structure recursively
            String[] Files;

            if (Dst[Dst.Length - 1] != Path.DirectorySeparatorChar)
                Dst += Path.DirectorySeparatorChar;
            if (!Directory.Exists(Dst)) Directory.CreateDirectory(Dst);
            Files = Directory.GetFileSystemEntries(Src);
            foreach (string Element in Files)
            {
                // Sub directories
                if (Directory.Exists(Element))
                    copyDirectory(Element, Dst + Path.GetFileName(Element));
                // Files in directory
                else
                    File.Copy(Element, Dst + Path.GetFileName(Element), true);
            }
        }

ASPX端代码：

                    <asp:Panel ID="pnlAddNewTemplate" runat="server" Width="280px" Height="200px" CssClass="popup">
                        <asp:UpdatePanel ID="updPnlAddNewContact" runat="server" UpdateMode="Conditional">
                            <ContentTemplate>
                                <div class="contact-inline">
                                    <span>Quote Folder - </span>
                                    <asp:HyperLink ID="hlTemplateQuoteFolder" runat="server" /></div>
                                 <telerik:RadTreeView ID="rtvTemplateFilesList" runat="server" CheckBoxes="true" OnClientNodeChecked="AfterCheck">    
                                </telerik:RadTreeView>
                                <asp:Label ID="test" runat="server" />
                                <div class="contact-inline">
                                    <asp:Button ID="btnAddNewTemplate" runat="server" Text="Add Template" OnClick="btnAddNewTemplate_Click" />
                                    <asp:Button ID="btnCancelNewTemplate" runat="server" Text="Cancel" OnClick="btnCancelNewTemplate_Click" />
                                </div>
                            </ContentTemplate>
                        </asp:UpdatePanel>
                    </asp:Panel>

还要在旁边加上一个JAVA SCRIPT的函数，用来监测当CHILD NODE被选中的话，PARENT NODE也要被同时选上

<%--If the node is checked, the childs of this node will also be checked--%>
                                 <script type="text/javascript">
                //<!--
                function UpdateAllChildren(nodes, checked)
                {
                    for (var i=0; i < nodes.get_count(); i++)
                    {
                        var node = nodes.getNode(i);
                        node.set_checked(checked);
                        UpdateAllChildren(node.get_nodes(), checked);       
                    }
                }

                function AfterCheck(treeView, args)
                {
                    var node = args.get_node();
                   
                    if (!node.get_checked() && node.get_parent() != treeView)
                    {
                        node.get_parent().set_checked(false);
                    }
//                    if(node.get_checked())
//                    {
//                        node.get_parent().set_checked(true);
//                    }
        
                    var siblingNodes = node.get_parent().get_nodes();
        
                    var allChecked = true;
                    for (var i = 0; i < siblingNodes.get_count(); i++)
                    {
                        var siblingNode = siblingNodes.getNode(i);
                        if (!siblingNode.get_checked())
                        {
                            allChecked = false;
                            break;
                        }
                    }
                   
                    if (allChecked && node.get_parent() != treeView)
                    {
                        node.get_parent().set_checked(true);
                    }
                   
                    UpdateAllChildren(node.get_nodes(), node.get_checked());
                }
               
                //-->
        </script>

最后么，你可以在WEB.config里面预设文件夹的位置

 <appSettings>
  <add key="ShowCustomErrors" value="false"/>
  <add key="FolderPath" value="c:\test\"/>
  <!-- root path of dst folders -->
  <add key="TemplatePath" value="c:\template\"/>
  <!-- root path of tempaltes -->
   </appSettings>

一个客户一定要实现这个功能，可是自从IE6的SP1后因为安全问题就被锁掉了。到了XP SP2后更是从OS层锁了。网上发现了个解法，当然不够安全。至少能SOLVE问题先 

Symptom Problem opening up local files in a Internet Explorer window. For example, the following code works on some systems and does not work in some. Test Explanation / Wor

Symptom Problem opening up local files in a Internet Explorer window. For example, the following code works on some systems and does not work in some. <a href="C:\Filename.TXT" target="_blank">Test</a> Explanation / Workaround: from Eric Shen [MS] The issue is a new security feature in Internet Explore 6 Service Pack 1. In order to prevent Internet vicious codes from accessing your local files, the development team developed the new security feature and included it in IE6 SP1. Please be advised that this is a normal behavior. Actually, IE6 SP1 includes new security code checks that prevent "zone elevation". This means that documents located in the "Internet" zone will not be granted access (through HREFs, scripting...etc) to documents in the "My Computer" zone. Only documents located in the "Trusted" or "My Computer" zone can access documents in the "My Computer" zone. Therefore, if you want to allow untrusted documents to access documents in the "My Computer" zone, you might add the source URL in "Trusted sites" (this must be done with caution for obvious security reasons). The "Local Intranet" zone is trusted as well. Furthermore, the following registry key allows disabling the new security codes check that prevent "zone elevation": - You can create this DWORD key and set it zero to disable this new feature. Also, you can enable it by changing it to 1 at any time. HKCU\Software\Microsoft\Internet Explorer\Main Disable_Local_Machine_Navigate = 0 (REG_DWORD) It is not recommended to use above registry key since it breaks the "zone elevation" security fix. Please use this tweak only if you have a valid reason to do so. The above is a per-user setting.

(XP Service Pack 2) Local Machine restrictions prevents even the Trusted sites from opening files in My Computer Zone

In Windows XP Service Pack 2, no site from any Zone can open files in local machine zone, whereas in pre-SP2, only Internet Zone sites were restricted to open local files, while Trusted/Intranet can.

While the above method (Disable_Local_Machine_Navigate) works fine in Windows XP Service Pack 2 also, here is more information and another workaround for this issue: