在C#程序中实现插件架构(2)

public interface IPlug
{
IPlugData GetData();
PlugDataEditControl GetEditControl(IPlugData Data);
bool Save(string Path);
bool Print(PrintDocument Document);
}

AttributeUsage(AttributeTargets.Class)
public class PlugDisplayNameAttribute : System.Attribute
{
private string _displayName;
public PlugDisplayNameAttribute(string DisplayName) : base()
{
_displayName=DisplayName;
return;
}
public override string ToString()
{
return _displayName;
}

PlugDisplayName("Employees")
PlugDescription("This plug is for managing employee data")
public class EmployeePlug : System.Object, IPlug
{
public IPlugData GetData()
{
IPlugData data = new EmployeeData
{
new EmployeeData("Jerry", "Seinfeld")
,new EmployeeData("Bill", "Cosby")
,new EmployeeData("Martin", "Lawrence")
};
return data;
}
public PlugDataEditControl GetEditControl(IPlugData Data)
{
return new EmployeeControl((EmployeeData)Data);
}
public bool Save(string Path)
{
//implementation not shown
}
public bool Print(PrintDocument Document)
{
//implementation not shown
}
}

private void LoadPlugs()
{
string files = Directory.GetFiles("Plugs", "*.plug");
foreach(string f in files)
{
try
{
Assembly a = Assembly.LoadFrom(f);
System.Type types = a.GetTypes();
foreach(System.Type type in types)
{
if(type.GetInterface("IPlug")!=null)
{
if(type.GetCustomAttributes(typeof(PlugDisplayNameAttribute),
false).Length!=1)
throw new PlugNotValidException(type,
"PlugDisplayNameAttribute is not supported");
if(type.GetCustomAttributes(typeof(PlugDescriptionAttribute),
false).Length!=1)
throw new PlugNotValidException(type, 
"PlugDescriptionAttribute is not supported");
_tree.Nodes.Add(new PlugTreeNode(type));
}
}
}
catch(Exception e)
{
MessageBox.Show(e.Message);
}
}
return;
}