write a custum class

Posted on 2006-02-23 13:55 舞步者阅读(288) 评论(0) 收藏举报

    In this post, ghj mentioned a few problems about using ConfigurationSettings.AppSettings[""] in our web or windows forms applications.
    The config files are only loaded when an application loads, so any changes in it will not take effect immediately.
    For web application, asp.net restarts the application any time the config file changes, ghj think it doesn't matter, but I can't say that I agree with him, In fact, restarting the application has a couple of bad effects, i.e. the application loses its cache and session state.
    For windows application, only one thing you can do is that prompte the user to reboot the application

I found a solution to this problem, Just write a custom class that would give me access to a configuration file, Ok, Let's start it.

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1using System;
            2using System.IO;
            3using System.Xml;
            4using System.Configuration;
            5
            6namespace Custom
            7{
            8 /// <summary>
            9 /// Provides a global Settings mechanism
            10 /// </summary>
            11 public class Settings
            12 {
            13  private XmlDocument configSource;
            14  private string xpathTemplate;
            15  private FileSystemWatcher configWatcher;
            16  private string configpath;
            17
            18
            19  /// <summary>
            20  /// Loads the config file ... private so you can't instantiate this object
            21  /// </summary>
            22  private Settings()
            23  {
            24   configSource = null;
            25   xpathTemplate = "//configuration/appSettings/add[@key='{0}']";
            26   configpath = string.Empty;
            27
            28   LoadconfigSource();
            29
            30   configWatcher = new FileSystemWatcher(Path.GetDirectoryName(this.configpath),
            31    Path.GetFileName(this.configpath));
            32   configWatcher.Changed +=new FileSystemEventHandler(watcher_Changed);
            33  }
            34
            35  /// <summary>
            36  /// Gets or Sets the value of a //configuration/appSettings/add node
            37  /// </summary>
            38  public string this[string key]
            39  {
            40   get
            41   {
            42    string xpath = string.Format(this.xpathTemplate,key);
            43    XmlNodeList nodes = configSource.SelectNodes(xpath);
            44
            45    if (nodes.Count <= 0)
            46     return null;
            47
            48    if (nodes.Count > 1)
            49     throw new Exception("Ambiguous key in config file");
            50
            51    string addvalue = nodes[0].Attributes["value"].InnerText;
            52    return addvalue;
            53   }
            54   set
            55   {
            56    string xpath = string.Format(this.xpathTemplate,key);
            57    XmlNodeList nodes = configSource.SelectNodes(xpath);
            58
            59    if (nodes.Count > 1)
            60     throw new Exception("Ambiguous key in config file");
            61
            62    if (nodes.Count <= 0)
            63    {//insert
            64
            65     XmlAttribute keyattrib = configSource.CreateAttribute("key");
            66     keyattrib.InnerText = key;
            67     XmlAttribute valattrib = configSource.CreateAttribute("value");
            68     valattrib.InnerText = value;
            69
            70     XmlNode add = configSource.CreateElement("add");
            71     add.Attributes.Append(keyattrib);
            72     add.Attributes.Append(valattrib);
            73
            74     XmlNode appsettings = configSource.GetElementsByTagName("appSettings")[0];
            75     appsettings.AppendChild(add);
            76    }
            77    else //edit
            78    {
            79     nodes[0].Attributes["value"].InnerText = value;
            80    }
            81
            82    //persist changes
            83    configSource.Save(this.configpath);
            84   }
            85  }
            86
            87  /// <summary>
            88  /// Loads the config file into memory
            89  /// </summary>
            90  private void LoadconfigSource()
            91  {
            92   System.Diagnostics.Debug.Write("Loading the config file");
            93   string dllpath = System.Reflection.Assembly.GetExecutingAssembly().Location;
            94   string filename = ConfigurationSettings.AppSettings["configfile"].ToString();
            95   configpath = string.Format(@"{0}\{1}",Path.GetDirectoryName(dllpath),filename);
            96   configSource = new XmlDocument();
            97
            98   Stream cstream = null;
            99
            100   //Attempt to open and load the configuration file
            101   try
            102   {
            103    cstream = (Stream)File.OpenRead(configpath);
            104    configSource.Load(cstream);
            105   }
            106   catch (FileNotFoundException fnfe)
            107   {
            108    throw fnfe;
            109   }
            110   catch (FileLoadException fle)
            111   {
            112    throw fle;
            113   }
            114   catch (XmlException xe)
            115   {
            116    throw xe;
            117   }
            118   catch (Exception e)
            119   {
            120    throw e;
            121   }
            122   finally
            123   {
            124    //make sure if the file stream get's opened that we close it.
            125    if (cstream != null)
            126     cstream.Close();
            127   }
            128  }
            129
            130  /// <summary>
            131  /// this event is triggered by the FileSystemWatcher.Changed event
            132  /// </summary>
            133  private void watcher_Changed(object sender, FileSystemEventArgs e)
            134  {
            135   LoadconfigSource();
            136  }
            137
            138  private static Settings privateInstance = null;
            139
            140  /// <summary>
            141  /// Gets a global instance of the Settings object
            142  /// </summary>
            143  public static Settings Instance
            144  {
            145   get
            146   {
            147    if (privateInstance == null)
            148     privateInstance = new Settings();
            149
            150    return privateInstance;
            151   }
            152  }
            153 }
            154}

using System;

            using System.IO;

            using System.Xml;

            using System.Configuration;

            namespace Custom

            {

            /// 
            /// Provides a global Settings mechanism
            /// 
            public class Settings
            {
            private XmlDocument configSource;
            private string xpathTemplate;
            private FileSystemWatcher configWatcher;
            private string configpath;
            /// 
            /// Loads the config file ... private so you can't instantiate this object
            /// 
            private Settings()
            {
            configSource = null;
            xpathTemplate = "//configuration/appSettings/add[@key='{0}']";
            configpath = string.Empty;
            LoadconfigSource();
            configWatcher = new FileSystemWatcher(Path.GetDirectoryName(this.configpath),
            Path.GetFileName(this.configpath));
            configWatcher.Changed +=new FileSystemEventHandler(watcher_Changed);
            }
            /// 
            /// Gets or Sets the value of a //configuration/appSettings/add node
            /// 
            public string this[string key]
            {
            get
            {
            string xpath = string.Format(this.xpathTemplate,key);
            XmlNodeList nodes = configSource.SelectNodes(xpath);
            if (nodes.Count <= 0)
            return null;
            if (nodes.Count > 1)
            throw new Exception("Ambiguous key in config file");
            string addvalue = nodes[0].Attributes["value"].InnerText;
            return addvalue;
            }
            set
            {
            string xpath = string.Format(this.xpathTemplate,key);
            XmlNodeList nodes = configSource.SelectNodes(xpath);
            if (nodes.Count > 1)
            throw new Exception("Ambiguous key in config file");
            if (nodes.Count <= 0)
            {//insert
            XmlAttribute keyattrib = configSource.CreateAttribute("key");
            keyattrib.InnerText = key;
            XmlAttribute valattrib = configSource.CreateAttribute("value");
            valattrib.InnerText = value;
            XmlNode add = configSource.CreateElement("add");
            add.Attributes.Append(keyattrib);
            add.Attributes.Append(valattrib);
            XmlNode appsettings = configSource.GetElementsByTagName("appSettings")[0];
            appsettings.AppendChild(add);
            }
            else //edit
            {
            nodes[0].Attributes["value"].InnerText = value;
            }
            //persist changes
            configSource.Save(this.configpath);
            }
            }
            /// 
            /// Loads the config file into memory
            /// 
            private void LoadconfigSource()
            {
            System.Diagnostics.Debug.Write("Loading the config file");
            string dllpath = System.Reflection.Assembly.GetExecutingAssembly().Location;
            string filename = ConfigurationSettings.AppSettings["configfile"].ToString();
            configpath = string.Format(@"{0}\{1}",Path.GetDirectoryName(dllpath),filename);
            configSource = new XmlDocument();
            Stream cstream = null;
            /*
            Attempt to open and load the configuration file
            If an exception is found, throw it to make sure the
            user/developer is aware of the problem, but make sure
            to close the stream if it's open.
            */
            try
            {
            cstream = (Stream)File.OpenRead(configpath);
            configSource.Load(cstream);
            }
            catch (FileNotFoundException fnfe)
            {
            throw fnfe;
            }
            catch (FileLoadException fle)
            {
            throw fle;
            }
            catch (XmlException xe)
            {
            throw xe;
            }
            catch (Exception e)
            {
            throw e;
            }
            finally
            {
            //make sure if the file stream get's opened that we close it.
            if (cstream != null)
            cstream.Close();
            }
            }
            /// 
            /// this event is triggered by the FileSystemWatcher.Changed event
            /// 
            private void watcher_Changed(object sender, FileSystemEventArgs e)
            {
            LoadconfigSource();
            }
            #region Singleton Stuff
            private static Settings privateInstance = null;
            /// 
            /// Gets a global instance of the Settings object
            /// 
            public static Settings Instance
            {
            get
            {
            if (privateInstance == null)
            privateInstance = new Settings();
            return privateInstance;
            }
            }
            #endregion
            }
            }

How to use this, All you have to do is provide an add node in either your app.config or web.config file that points to the config file you want to use.

<configuration>

  <appSettings>

    <add key="configfile" value="my.config"/>

  </appSettings>

</configuration>

Note : This file path is relative to the exe or dll that contains the class. If you were using this file in a web application, you'd have to use "..\my.config".

posted on 2004-05-27 11:49 fengzhimei 阅读(1444) 评论(5) 编辑收藏收藏至365Key 所属分类: Asp.net 、Code Snippet

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# re: 2004-05-27 12:57 陈叙远

使用System.Web.Caching.CacheDependency关联config就可以了吧回复

# re: Write a custom config class. 2004-05-27 13:28 fengzhimei

yes,That's for sure in theory.
you can store your own items in a custom config file and use your own CacheDependency to monitor changes,but i never test:) 回复

# Another way to retrieve a custom key's value from web.config in web form application[TrackBack] 2004-05-27 14:21 Fengzhimei@Dot.Net

Another way to retrieve a custom key's value from web.config in web form application
Fengzhimei@Dot.Net引用了该文章,地址:http://www.cnblogs.com/fengzhimei/archive/2004/05/27/11780.aspx 回复

# re: Write a custom config class. 2004-05-27 14:39 ghj1976

1、如果是 Web 应用程序，它并不是在当前路径下执行的：

Path.GetDirectoryName(dllpath)
返回的是：
@"c:\windows\microsoft.net\framework\v1.1.4322\temporary asp.net files\testweb\02da89a5\6e4314f7\assembly\dl2\beeff702\089d3d91_b443c401"
而不是你需要的路径

应该为：
AppDomain.CurrentDomain.BaseDirectory
回复

# re: Write a custom config class. 2004-05-27 14:44 ghj1976

2、 Web 应用程序我试验了你上面的代码，在 my.config 被修改的时候，并不会触发 watcher_Changed ，这应该是 Web 应用程序的运行机制所决定的。

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write a custum class

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