利用属性(Attribute)扩展元数据,关于自定义配置节(转载)

介绍
    在NET中可以用自己的 XML 配置元素来扩展标准的 ASP.NET 配置设置集。若要完成该操作，必须一个实现 System.Configuration.ConfigurationSection 类的 .NET Framework 类。
    netframework 主要包括一下处理程序:
    SingleTagSectionHandler 配置节返回类型为 Systems.Collections.IDictionary
    DictionarySectionHandler 配置节返回类型为 Systems.Collections.IDictionary
    NameValueSectionHandler 配置节返回类型为 Systems.Collections.Specialized.NameValueCollection

创建自定义配置节

    1、在<configSections/>中声明配置节，
    2、在<Custom element for configuration section>处设置配置节的具体配置。
    3、访问自定义配置数据

实现 ConfigurationSection 类创建自定义配置文件处理类

    1、实现配置文件处理程序.
    2、创建配置文件
    3、访问配置信息。
    
示例代码
    创建控制台应用程序ConfigSections
    1、App.config

1. <?xml version="1.0" encoding="utf-8" ?>
2. <configuration>
3.     <configSections>
4.         <section name="SingleTagSection" type="System.Configuration.SingleTagSectionHandler"/>
5.         <section name="DictionarySection" type="System.Configuration.DictionarySectionHandler"/>
6.         <section name="NameValueSection" type="System.Configuration.NameValueSectionHandler" />
7.         <section  name="CustomSection" type="ConfigSections.CustomSection,ConfigSections"   />
8.        
9.     </configSections>
10.     <SingleTagSection setting1="One world" setting2=" one dream"  />
11.     <DictionarySection>
12.         <add key="China" value="51" />
13.         <add key="USA" value="36" />
14.         <add key="RUS" value="23" />
15.     </DictionarySection>
16.     <NameValueSection>
17.         <add key="China" value="100" />
18.         <add key="USA" value="110" />
19.         <add key="RUS" value="72" />
20.     </NameValueSection>
21.     <CustomSection fileName="default.txt" maxUsers="1000" maxIdleTime="00:15:00" />
22. </configuration>

    2、CustomSection.cs

1. // Define a custom section.
2. // The CustomSection type alows to define a custom section 
3. // programmatically.
4. using System.Configuration;
5. using System;
6. namespace ConfigSections
7. {
8.     public sealed class CustomSection : ConfigurationSection
9.     {
10.         // The collection (property bag) that conatains 
11.         // the section properties.
12.         private static ConfigurationPropertyCollection _Properties;
14.         // Internal flag to disable 
15.         // property setting.
16.         private static bool _ReadOnly;
18.         // The FileName property.
19.         private static readonly ConfigurationProperty _FileName =
20.             new ConfigurationProperty("fileName",
21.             typeof(string), "default.txt",
22.             ConfigurationPropertyOptions.IsRequired);
24.         // The MasUsers property.
25.         private static readonly ConfigurationProperty _MaxUsers =
26.             new ConfigurationProperty("maxUsers",
27.             typeof(long), (long)1000,
28.             ConfigurationPropertyOptions.None);
30.         // The MaxIdleTime property.
31.         private static readonly ConfigurationProperty _MaxIdleTime =
32.             new ConfigurationProperty("maxIdleTime",
33.             typeof(TimeSpan), TimeSpan.FromMinutes(5),
34.             ConfigurationPropertyOptions.IsRequired);
36.         // CustomSection constructor.
37.         public CustomSection()
38.         {
39.             // Property initialization
40.             _Properties =
41.                 new ConfigurationPropertyCollection();
43.             _Properties.Add(_FileName);
44.             _Properties.Add(_MaxUsers);
45.             _Properties.Add(_MaxIdleTime);
46.         }
49.         // This is a key customization. 
50.         // It returns the initialized property bag.
51.         protected override ConfigurationPropertyCollection Properties
52.         {
53.             get
54.             {
55.                 return _Properties;
56.             }
57.         }
60.         private new bool IsReadOnly
61.         {
62.             get
63.             {
64.                 return _ReadOnly;
65.             }
66.         }
68.         // Use this to disable property setting.
69.         private void ThrowIfReadOnly(string propertyName)
70.         {
71.             if (IsReadOnly)
72.                 throw new ConfigurationErrorsException(
73.                     "The property " + propertyName + " is read only.");
74.         }
77.         // Customizes the use of CustomSection
78.         // by setting _ReadOnly to false.
79.         // Remember you must use it along with ThrowIfReadOnly.
80.         protected override object GetRuntimeObject()
81.         {
82.             // To enable property setting just assign true to
83.             // the following flag.
84.             _ReadOnly = true;
85.             return base.GetRuntimeObject();
86.         }
89.         [StringValidator(InvalidCharacters = " ~!@#$%^&*()[]{}/;'\"|\\",
90.             MinLength = 1, MaxLength = 60)]
91.         public string FileName
92.         {
93.             get
94.             {
95.                 return (string)this["fileName"];
96.             }
97.             set
98.             {
99.                 // With this you disable the setting.
100.                 // Renemmber that the _ReadOnly flag must
101.                 // be set to true in the GetRuntimeObject.
102.                 ThrowIfReadOnly("FileName");
103.                 this["fileName"] = value;
104.             }
105.         }
107.         [LongValidator(MinValue = 1, MaxValue = 1000000,
108.             ExcludeRange = false)]
109.         public long MaxUsers
110.         {
111.             get
112.             {
113.                 return (long)this["maxUsers"];
114.             }
115.             set
116.             {
117.                 this["maxUsers"] = value;
118.             }
119.         }
121.         [TimeSpanValidator(MinValueString = "0:0:30",
122.             MaxValueString = "5:00:0",
123.             ExcludeRange = false)]
124.         public TimeSpan MaxIdleTime
125.         {
126.             get
127.             {
128.                 return (TimeSpan)this["maxIdleTime"];
129.             }
130.             set
131.             {
132.                 this["maxIdleTime"] = value;
133.             }
134.         }
137.     }
138. }

    3、Program.cs

1. using System;
2. using System.Collections.Generic;
3. using System.Linq;
4. using System.Text;
5. using System.Configuration;
6. using System.Collections.Specialized;
7. using System.Collections;
9. namespace ConfigSections
10. {
11.     class Program
12.     {
13.         static void Main(string[] args)
14.         {
15.             IDictionary dictionary = ConfigurationManager.GetSection("SingleTagSection") as IDictionary;
16.             foreach (DictionaryEntry item in dictionary)
17.             {
18.                 Console.Write(item.Value);
19.             }
21.             Console.WriteLine();
23.             dictionary = ConfigurationManager.GetSection("DictionarySection") as IDictionary;
24.             foreach (DictionaryEntry item in dictionary)
25.             {
26.                 Console.WriteLine("{0}\t{1}", item.Key, item.Value);
27.             }
29.             Console.WriteLine();
30.             NameValueCollection nameValueCollection = ConfigurationManager.GetSection("NameValueSection") as NameValueCollection;
31.             foreach (string key in nameValueCollection.AllKeys)
32.             {
33.                 Console.WriteLine("{0}\t{1}", key, nameValueCollection[key]);
34.             }
35.             CustomSection section = ConfigurationManager.GetSection("CustomSection") as CustomSection;
36.             Console.WriteLine(section.FileName);
37.             Console.WriteLine(section.MaxUsers);
38.             Console.ReadLine();
39.         }
40.     }
41. }