在前一篇文章中，讲述了配置应用程序块的最简单的介绍，在本篇文章中我主要介绍一下配置应用程序块的响应配置变更通知，保护配置信息（加密配置信息），面向高级人员的扩展机制，配置数据的缓存等几个方面。在剖析篇中我会去分析配置应用程序块的底层设计及类设计。
一．响应配置变更通知：
Configuration Application Block
提供了一个事件机制，当存储的配置变更时通知应用程序
，使用步骤：
1）创建一个EverntHandler
1
/// <summary>
2
/// 创建EventHanler
3 /// </summary>
4 /// <param name="sender"></param>
5
/// <param name="args"></param>
6
private
void
OnConfigurationChanged(
object
sender, ConfigurationChangedEventArgs args)
7
{
8 Cursor = System.Windows.Forms.Cursors.WaitCursor;
9
10 EditorFontData configData = ConfigurationManager.GetConfiguration("EditorSettings") as EditorFontData;
11
12 StringBuilder results = new StringBuilder();
13 results.Append("Configuration changes in storage were detected. Updating configuration.");
14 results.Append(Environment.NewLine);
15 results.Append("New configuration settings:");
16 results.Append(Environment.NewLine);
17 results.Append('\t');
18 results.Append(configData.ToString());
19 results.Append(Environment.NewLine);
20
21 Cursor = System.Windows.Forms.Cursors.Arrow;
22 }
/// <summary>2
/// 创建EventHanler3
/// </summary>4
/// <param name="sender"></param>5
/// <param name="args"></param>
6
private
void
OnConfigurationChanged(
object
sender, ConfigurationChangedEventArgs args)7
{8
Cursor = System.Windows.Forms.Cursors.WaitCursor;9
10
EditorFontData configData = ConfigurationManager.GetConfiguration("EditorSettings") as EditorFontData;11
12
StringBuilder results = new StringBuilder(); 13
results.Append("Configuration changes in storage were detected. Updating configuration.");14
results.Append(Environment.NewLine);15
results.Append("New configuration settings:");16
results.Append(Environment.NewLine);17
results.Append('\t');18
results.Append(configData.ToString());19
results.Append(Environment.NewLine);20
21
Cursor = System.Windows.Forms.Cursors.Arrow; 22
}
2）注册事件
1
///注册事件
2
ConfigurationManager.ConfigurationChanged
+=
new
ConfigurationChangedEventHandler(OnConfigurationChanged);
///注册事件
2
ConfigurationManager.ConfigurationChanged
+=
new
ConfigurationChangedEventHandler(OnConfigurationChanged);
二．配置数据的缓存：
Configuration Application Block
在设计时提供了对配置数据的缓存，在读取
XML
数据后，再次读取它首先会判断缓存是否为空，如果不为空，它会直接从缓存中读取数据（在剖析篇中会有详细的介绍）。
显式的清除掉缓存用下面这句代码即可：
1
///清除缓存数据
2
ConfigurationManager.ClearSingletonSectionCache();
///清除缓存数据
2
ConfigurationManager.ClearSingletonSectionCache();
三．面向高级人员的扩展机制：
1
．
除了用
XML
文件可以存储数据外，还可以创建自己的存储方式，像
SQL Server Database
，注册表存储等，这时就需要我们自己创建
StorageProvider
。创建自定义的
Storage Provider
，需要注意以下几点：
1
）要读取和写入数据，需要继承于
StorageProvider
类和分别实现
IStorageProviderReader
和
IstorageProviderWriter
接口：
1
public
class
XmlFileStorageProvider : StorageProvider, IStorageProviderWriter
2
{
3 //……
4 }
public
class
XmlFileStorageProvider : StorageProvider, IStorageProviderWriter2
{3
//……4
}
2
）如果实现了
IConfigurationProvider
接口，则方法
Initialize()
就不能为空，也必须实现：
1
public
override
void
Initialize(ConfigurationView configurationView)
2
{
3 //……
4 }
public
override
void
Initialize(ConfigurationView configurationView)2
{3
//……4
}
3
）实现
Read()
和
Write()
方法，记住一定要返回类型为
object
，否则
Transformer
将无法使用：
1
public
override
object
Read()
2
{
3 //……
4 }
5
6
public
void
Write(
object
value)
7
{
8 //……
9 }
public
override
object
Read()2
{3
//……4
}
5
6
public
void
Write(
object
value)7
{8
//……9
}
2
．创建自定义的
Transformer
如果我们创建的自定义的
Storage Provider
不能后支持
XMLNode
，这时候我们需要创建自己的
Transformer
，需要注意以下几点：
1
）自定义的
Transformer
如果实现了
Itransformer
接口；则必须实现方法
Serialize()
和
Deserialize()；
2
）自定义的
Transformer
如果实现了
IConfigurationProvider
接口，则方法
Initialize()
就不能为空，也必须实现；
下面给出一个
SoapSerializerTransformer
的例子程序（先声名一下，这个例子程序不是我写的，而是Dario Fruk先生^_^）：
1
namespace
idroot.Framework.Configuration
2
{
3 using System;
4 using System.Configuration;
5 using System.IO;
6 using System.Runtime.Serialization.Formatters.Soap;
7 using System.Text;
8 using System.Xml;
9
10 using Microsoft.Practices.EnterpriseLibrary.Common;
11 using Microsoft.Practices.EnterpriseLibrary.Configuration;
12
13
/// <summary>
14 /// SoapSerializerTransformer is a custom Serialization Transformer for Microsft Enterprise Library 1.0.
15
/// </summary>
16 public class SoapSerializerTransformer : TransformerProvider
17 {
18 public override void Initialize(ConfigurationView configurationView)
19 {
20 // Do nothing. This implementation does not require any additional configuration data because SoapFormatter reflects types
21 // during serialization.
22 }
23
24 public override object Serialize(object value)
25 {
26 SoapFormatter soapFormatter = new SoapFormatter();
27 StringBuilder stringBuilder = new StringBuilder();
28 XmlDocument doc = new XmlDocument();
29
30 stringBuilder.Append("<soapSerializerSection>");
31
32 string serializedObject = "";
33 using (MemoryStream stream = new MemoryStream())
34 {
35 soapFormatter.Serialize(stream, value);
36 byte[] buffer = stream.GetBuffer();
37 // quick fix for 0-byte padding
38 serializedObject = ASCIIEncoding.ASCII.GetString(buffer).Replace('\0', ' ').Trim();
39 }
40 stringBuilder.Append(serializedObject);
41
42 stringBuilder.Append("</soapSerializerSection>");
43 doc.LoadXml(stringBuilder.ToString());
44
45 return doc.DocumentElement;
46 }
47
48 public override object Deserialize(object section)
49 {
50 ArgumentValidation.CheckForNullReference(section, "section");
51 ArgumentValidation.CheckExpectedType(section, typeof(XmlNode));
52
53 XmlNode sectionNode = (XmlNode)section;
54
55 XmlNode serializedObjectNode = sectionNode.SelectSingleNode("//soapSerializerSection");
56 if (serializedObjectNode == null)
57 {
58 throw new ConfigurationException("The required element '<soapSerializationSection>' missing in the specified Xml configuration file.");
59 }
60
61 SoapFormatter soapFormatter = new SoapFormatter();
62 try
63 {
64 object obj = null;
65 using (MemoryStream stream = new MemoryStream())
66 {
67 using (StreamWriter sw = new StreamWriter(stream, Encoding.ASCII))
68 {
69 sw.Write(serializedObjectNode.InnerXml);
70 sw.Flush();
71 // rewind stream to the begining or deserialization will throw Exception.
72 sw.BaseStream.Seek(0, SeekOrigin.Begin);
73 obj = soapFormatter.Deserialize(stream);
74 }
75 }
76 return obj;
77 }
78 catch (InvalidOperationException e)
79 {
80 string message = e.Message;
81 if (null != e.InnerException)
82 {
83 message = String.Concat(message, " ", e.InnerException.Message);
84 }
85 throw new ConfigurationException(message, e);
86 }
87 }
88 }
89}
namespace
idroot.Framework.Configuration2
{3
using System;4
using System.Configuration;5
using System.IO;6
using System.Runtime.Serialization.Formatters.Soap;7
using System.Text;8
using System.Xml;9
10
using Microsoft.Practices.EnterpriseLibrary.Common;11
using Microsoft.Practices.EnterpriseLibrary.Configuration;12
13
/// <summary>14
/// SoapSerializerTransformer is a custom Serialization Transformer for Microsft Enterprise Library 1.0.15
/// </summary>16
public class SoapSerializerTransformer : TransformerProvider17
{ 18
public override void Initialize(ConfigurationView configurationView)19
{20
// Do nothing. This implementation does not require any additional configuration data because SoapFormatter reflects types 21
// during serialization.22
}23
24
public override object Serialize(object value)25
{26
SoapFormatter soapFormatter = new SoapFormatter();27
StringBuilder stringBuilder = new StringBuilder();28
XmlDocument doc = new XmlDocument();29
30
stringBuilder.Append("<soapSerializerSection>");31
32
string serializedObject = "";33
using (MemoryStream stream = new MemoryStream())34
{35
soapFormatter.Serialize(stream, value);36
byte[] buffer = stream.GetBuffer();37
// quick fix for 0-byte padding38
serializedObject = ASCIIEncoding.ASCII.GetString(buffer).Replace('\0', ' ').Trim();39
}40
stringBuilder.Append(serializedObject);41
42
stringBuilder.Append("</soapSerializerSection>");43
doc.LoadXml(stringBuilder.ToString());44
45
return doc.DocumentElement;46
}47
48
public override object Deserialize(object section)49
{50
ArgumentValidation.CheckForNullReference(section, "section");51
ArgumentValidation.CheckExpectedType(section, typeof(XmlNode));52
53
XmlNode sectionNode = (XmlNode)section;54
55
XmlNode serializedObjectNode = sectionNode.SelectSingleNode("//soapSerializerSection");56
if (serializedObjectNode == null)57
{58
throw new ConfigurationException("The required element '<soapSerializationSection>' missing in the specified Xml configuration file.");59
}60
61
SoapFormatter soapFormatter = new SoapFormatter();62
try63
{64
object obj = null;65
using (MemoryStream stream = new MemoryStream())66
{67
using (StreamWriter sw = new StreamWriter(stream, Encoding.ASCII))68
{69
sw.Write(serializedObjectNode.InnerXml);70
sw.Flush();71
// rewind stream to the begining or deserialization will throw Exception.72
sw.BaseStream.Seek(0, SeekOrigin.Begin); 73
obj = soapFormatter.Deserialize(stream);74
}75
}76
return obj;77
}78
catch (InvalidOperationException e)79
{80
string message = e.Message;81
if (null != e.InnerException)82
{83
message = String.Concat(message, " ", e.InnerException.Message);84
}85
throw new ConfigurationException(message, e);86
}87
}88
}89
}
3
．使用其它的
Providers
SQL Server Provider
：使用数据库
SQL Server Provider
Registry Provider
：使用注册表
Provider
四．保护配置信息：
配置信息直接放在了
XML
文件里面是不安全，我们可以用加密应用程序块对其进行加密，其实对于所有的应用程序块的配置信息都可以进行加密，我们到加密应用程序块时再详细讨论：）
进阶篇就写到这里了，后面继续剖析篇，在剖析篇里我会从配置应用程序块的底层设计，到类设计等作一些介绍（个人理解
^_^
）
本文转自lihuijun51CTO博客，原文链接：
http://blog.51cto.com/terrylee/67600
，如需转载请自行联系原作者
