首先解决的就是插件放在什么地方，我采取的传统的方法，将插件放到应用程序所在目录下的制定目录，我会在应用程序所在的目录下创建一个文件夹，命名为Plugins。接下来的工作就是要通知哪些插件是要加载的，哪些是不需要加载的，我会将这些信息放到应用程序的配置文件中的制定配置块中，当应用程序运行的时候，就会读取配置文件，并根据获得的信息加载插件。另外我们的应用程序框架是建立在Service基础之上，所以我需要创建一个管理插件的service。
我们现在定义一个插件管理的Service接口。
复制 
保存using System;
using System.Collections.Generic;
using System.Text;
namespace PluginFramework
{
public interface IPluginService
{
IApplication Application { get; set; }
void AddPlugin(String pluginName, String pluginType, String Assembly, String pluginDescription);
void RemovePlugin(String pluginName);
String[] GetAllPluginNames();
Boolean Contains(String pluginName);
Boolean LoadPlugin(String pluginName);
Boolean UnLoadPlugin(String pluginName);
IPlugin GetPluginInstance(String pluginName);
void LoadAllPlugin();
}
}
PluginService要实现的目标首先是在配置文件中添加/删除要加载的插件以及相关的信息，接下来就是动态的加载插件。我们要定义几个类型：Plugin配置区块类型，Plugin元素类型，plugin元素集合类型，以便我们能够读取插件的信息。
最后我们实现PluginService：
复制 保存using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;
using System.Configuration;
using System.Reflection;
using System.Windows.Forms;
using System.IO;
using System.Collections;
namespace PluginFramework
{
public class PluginService : IPluginService
{
private IApplication application = null;
private PluginConfigurationSection config = null;
private Dictionary<String, IPlugin> plugins = new Dictionary<string, IPlugin>();
private XmlDocument doc = new XmlDocument();
public PluginService()
{
}
public PluginService(IApplication application)
{
this.application = application;
}
IPluginService Members#region IPluginService Members
public void AddPlugin(string pluginName, string pluginType, string assembly, string pluginDescription)
{
doc.Load(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);
XmlNode pluginNode = doc.SelectSingleNode("/configuration/PluginSection");
XmlElement ele = doc.CreateElement("add");
XmlAttribute attr = doc.CreateAttribute("Name");
attr.Value = pluginName;
ele.SetAttributeNode(attr);
XmlAttribute attrType = doc.CreateAttribute("Type");
attrType.Value = pluginType;
ele.SetAttributeNode(attrType);
XmlAttribute attrAss = doc.CreateAttribute("Assembly");
attrAss.Value = assembly;
ele.SetAttributeNode(attrAss);
XmlAttribute attrDes = doc.CreateAttribute("Description");
attrDes.Value = pluginDescription;
ele.SetAttributeNode(attrDes);
pluginNode.AppendChild(ele);
doc.Save(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);
ConfigurationManager.RefreshSection("PluginSection");
}
public void RemovePlugin(string pluginName)
{
doc.Load(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);
XmlNode node = doc.SelectSingleNode("/configuration/PluginSection");
foreach (XmlNode n in node.ChildNodes)
{
if (n.Attributes != null)
{
if (n.Attributes[0].Value == pluginName)
{
node.RemoveChild(n);
}
}
}
doc.Save(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);
ConfigurationManager.RefreshSection("PluginSection");
}
public string[] GetAllPluginNames()
{
config = (PluginConfigurationSection)ConfigurationManager.GetSection("PluginSection");
PluginConfigurationElement pe = new PluginConfigurationElement();
ArrayList ps = new ArrayList();
for (Int32 i = 0; i < config.PluginCollection.Count; i++)
{
pe = config.PluginCollection[i];
ps.Add(pe.Name);
}
return (String[])ps.ToArray(typeof(String));
}
public bool Contains(string pluginName)
{
config = (PluginConfigurationSection)ConfigurationManager.GetSection("PluginSection");
PluginConfigurationElement pe = new PluginConfigurationElement();
List<String> ps = new List<string>();
for (Int32 i = 0; i < config.PluginCollection.Count; i++)
{
pe = config.PluginCollection[i];
ps.Add(pe.Name);
}
return ps.Contains(pluginName);
}
public bool LoadPlugin(string pluginName)
{
Boolean result = false;
config = (PluginConfigurationSection)ConfigurationManager.GetSection("PluginSection");
PluginConfigurationElement pe = new PluginConfigurationElement();
String path = Path.GetDirectoryName(System.Windows.Forms.Application.ExecutablePath) + """Plugin";
try
{
for (Int32 i = 0; i < config.PluginCollection.Count; i++)
{
pe = config.PluginCollection[i];
if (pe.Name == pluginName)
{
Assembly assembly = Assembly.LoadFile(path + """" + pe.Assembly);
Type type = assembly.GetType(pe.Type);
IPlugin instance = (IPlugin)Activator.CreateInstance(type);
instance.Application = application;
instance.Load();
plugins[pluginName] = instance;
result = true;
break;
}
}
if (!result)
{
MessageBox.Show("Not Found the Plugin");
}
}
catch (Exception e)
{
MessageBox.Show(e.Message);
result = false;
}
return result;
}
public bool UnLoadPlugin(string pluginName)
{
Boolean result = false;
try
{
IPlugin plugin = GetPluginInstance(pluginName);
plugin.UnLoad();
result = true;
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
return result;
}
public void LoadAllPlugin()
{
PluginConfigurationElement pe = new PluginConfigurationElement();
config = (PluginConfigurationSection)ConfigurationManager.GetSection("PluginSection");
String path = Path.GetDirectoryName(System.Windows.Forms.Application.ExecutablePath) + """Plugin";
try
{
for (Int32 i = 0; i < config.PluginCollection.Count; i++)
{
pe = config.PluginCollection[i];
Assembly assembly = Assembly.LoadFile(path + """" + pe.Assembly);
Type type = assembly.GetType(pe.Type);
IPlugin instance = (IPlugin)Activator.CreateInstance(type);
instance.Application = application;
instance.Load();
plugins[pe.Name] = instance;
}
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
}
public IApplication Application
{
get
{
return application;
}
set
{
application = value;
}
}
public IPlugin GetPluginInstance(string pluginName)
{
IPlugin plugin = null;
if (plugins.ContainsKey(pluginName))
{
plugin = plugins[pluginName];
}
return plugin;
}
#endregion
}
}
由于代码比较多，我也就不一一列举了，只把比较重要的代码列出来，其余的我会提供源代码的下载。在实现了PluginService以后，我们需要有一个地方能够使用这个Service来管理插件，我的做法是在一个菜单里添加一个项目，当用户点击这个项目的时候弹出插件管理的对话框，用户在这个对话框中选择使用那些插件，当插件被选中的时候，插件会被立即加载进来，并且记录到配置文件里，当用户下次运行应用程序的时候，插件默认会被自动的加载。
另外从现在开始我们就需要使用配置文件了，所以，我们需要给应用程序添加一个app.config文件，文件内容如下：
复制 保存<?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <section name="PluginSection" type="PluginFramework.PluginConfigurationSection, PluginFramework" /> </configSections> <PluginSection> </PluginSection> </configuration>
样子，总体来说我们就为Plugin的管理提供了一个基本的实现，如果大家还有什么不明白的地方，可以参考我提供的源代码或者通过e-mail和我联系。
源代码下载
https://files.cnblogs.com/guanjinke/pluginsample2.rar
