C# AttributeUsage使用案例详解

using System;   
[AttributeUsage(AttributeTargets.Class), AllowMultiple = false, Inherited = false ]   
public class HelpAttribute : Attribute   
{   
    public HelpAttribute(String Description_in)
    {   
        this.description = Description_in;   
    }   
     protected String description;   
     public String Description {   
        get {   
            return this.description;   
        }   
    } 
}

[Help("this is a do-nothing class")]   
public class AnyClass   
{   
    [Help("this is a do-nothing method")] //error   
    public void AnyMethod()
    {   
    }   
} 

   Assembly,   
　　Module,   
　　Class,   
　　Struct,   
　　Enum,   
　　Constructor,   
　　Method,   
　　Property,   
　　Field,   
　　Event,   
　　Interface,   
　　Parameter,   
　　Delegate,   
　　All = Assembly | Module | Class |   
　　Struct | Enum | Constructor |   
　　Method | Property | Field | Event |   
　　Interface | Parameter | Delegate,   
　　ClaSSMembers = Class | Struct | Enum |  
　　 Constructor | Method | Property | Field |  
　　 Event | Delegate | Interface ) 

[Help("this is a do-nothing class")]   
[Help("it contains a do-nothing method")]   
public class AnyClass   
{   
    [Help("this is a do-nothing method")] //error   
    public void AnyMethod()
    {   
    } 
}  

[Help("BaseClass")]   
public class Base   
{   
}   
　　   
public class Derive : Base   
{   
} 

[Help("BaseClass")]   
public class Base   
{   
}   
　　   
public class Derive : Base   
{   
} 

[Help("BaseClass")]   
public class Base   
{   
}   
[Help("DeriveClass")]   
public class Derive : Base   
{   
}