关于.net componet和attributes，c#高手请进
最近在学C#,对.net componet和attributes的用途不是很清楚，他们的功能和特点是什么，一般应该在什么时候用，请指点一二。
这方面的书好像满少的，都是些介绍语法的，我觉得语法其实不重要，明白什么时候该用它才是重要的。
问题点数：100、回复次数：6Top
1 楼snewxf（心疤）回复于 2002-05-28 18:21:33 得分 50
attributes我理解为附加信息。
比如说一个方法或是类你要告诉别人他有什么功能。。。。你就用这个附加说明。然后用反射求出。。。
component是组件的意思。
组件是由类来实现的。但组件和类不同。组件必须实现。system.componentModel.IComponent接口，并且提供一个没有参数的构造函数！假如一个类实现了这个接口。那么他就成组件了。
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2 楼longbow74（）回复于 2002-05-29 10:34:19 得分 0
1.不知道system.componentModel.IComponent内部实现了什么，功能和原来的COM+有什么不同？
2.对用法还是不太明白，能结合一下MSDN的例子说一下吗？
// AttributesTutorial.cs
// This example shows the use of class and method attributes.
using System;
using System.Reflection;
using System.Collections;
// The IsTested class is a user-defined custom attribute class.
// It can be applied to any declaration including
// - types (struct, class, enum, delegate)
// - members (methods, fields, events, properties, indexers)
// It is used with no arguments.
public class IsTestedAttribute : Attribute
{
public override string ToString()
{
return "Is Tested";
}
}
// The AuthorAttribute class is a user-defined attribute class.
// It can be applied to classes and struct declarations only.
// It takes one unnamed string argument (the author's name).
// It has one optional named argument Version, which is of type int.
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
public class AuthorAttribute : Attribute
{
// This constructor specifies the unnamed arguments to the attribute class.
public AuthorAttribute(string name)
{
this.name = name;
this.version = 0;
}
// This property is readonly (it has no set accessor)
// so it cannot be used as a named argument to this attribute.
public string Name
{
get
{
return name;
}
}
// This property is read-write (it has a set accessor)
// so it can be used as a named argument when using this
// class as an attribute class.
public int Version
{
get
{
return version;
}
set
{
version = value;
}
}
public override string ToString()
{
string value = "Author : " + Name;
if (version != 0)
{
value += " Version : " + Version.ToString();
}
return value;
}
private string name;
private int version;
}
// Here you attach the AuthorAttribute user-defined custom attribute to
// the Account class. The unnamed string argument is passed to the
// AuthorAttribute class's constructor when creating the attributes.
[Author("Joe Programmer")]
class Account
{
// Attach the IsTestedAttribute custom attribute to this method.
[IsTested]
public void AddOrder(Order orderToAdd)
{
orders.Add(orderToAdd);
}
private ArrayList orders = new ArrayList();
}
// Attach the AuthorAttribute and IsTestedAttribute custom attributes
// to this class.
// Note the use of the 'Version' named argument to the AuthorAttribute.
[Author("Jane Programmer", Version = 2), IsTested()]
class Order
{
// add stuff here ...
}
class MainClass
{
private static bool IsMemberTested(MemberInfo member)
{
foreach (object attribute in member.GetCustomAttributes(true))
{
if (attribute is IsTestedAttribute)
{
return true;
}
}
return false;
}
private static void DumpAttributes(MemberInfo member)
{
Console.WriteLine("Attributes for : " + member.Name);
foreach (object attribute in member.GetCustomAttributes(true))
{
Console.WriteLine(attribute);
}
}
public static void Main()
{
// display attributes for Account class
DumpAttributes(typeof(Account));
// display list of tested members
foreach (MethodInfo method in (typeof(Account)).GetMethods())
{
if (IsMemberTested(method))
{
Console.WriteLine("Member {0} is tested!", method.Name);
}
else
{
Console.WriteLine("Member {0} is NOT tested!", method.Name);
}
}
Console.WriteLine();
// display attributes for Order class
DumpAttributes(typeof(Order));
// display attributes for methods on the Order class
foreach (MethodInfo method in (typeof(Order)).GetMethods())
{
if (IsMemberTested(method))
{
Console.WriteLine("Member {0} is tested!", method.Name);
}
else
{
Console.WriteLine("Member {0} is NOT tested!", method.Name);
}
}
Console.WriteLine();
}
}
Output
Attributes for : Account
Author : Joe Programmer
Member GetHashCode is NOT tested!
Member Equals is NOT tested!
Member ToString is NOT tested!
Member AddOrder is tested!
Member GetType is NOT tested!
Attributes for : Order
Author : Jane Programmer Version : 2
Is Tested
Member GetHashCode is NOT tested!
Member Equals is NOT tested!
Member ToString is NOT tested!
Member GetType is NOT tested!
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3 楼alpine（笨笨）回复于 2002-05-29 11:28:25 得分 50
昨天给你回了一篇，结果没有粘上，分特勒
Attribute的用处就是保存那些与类或者方法本身相关的，可是又不是类或者方法自身的东东。在Design Time（设计阶段，也可以认为是编码阶段）可以确定的，硬编码进去；在Run Time（运行阶段）可以读出，但是并不能修改（不太确定）。以前一般来说，这种工作都是放在配置文件中或者资源文件中进行保存的，如果不需要在运行阶段读出的话，可以放在注释中。现在都可以统一放在Attribute里面了。
例如：有些值需要保存在注册表中，在注册表中的位置是确定的，但也要易于修改。以前会放在字符串资源里面，或者单独有配置文件。现在都可以放在Attribute里面。上面的例子里面有Author的用法吧，以前是放在注释里面，现在可以放在Attribute里面。还有WebMethod，用Attribute说明是非常合适的。Top
4 楼longbow74（）回复于 2002-05-29 17:02:26 得分 0
有点点懂了，除了些文字性的说明如用法，版本，作者之类的东东一般还放什么东东？Top
5 楼longbow74（）回复于 2002-05-30 16:30:01 得分 0
component?Top
6 楼longbow74（）回复于 2002-05-31 10:07:30 得分 0
again?Top
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