示例

下面是集合所有部分的完整示例。

// 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();    }}

输出

Attributes for : AccountAuthor : Joe ProgrammerMember 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 : OrderAuthor : Jane Programmer Version : 2Is TestedMember GetHashCode is NOT tested!Member Equals is NOT tested!Member ToString is NOT tested!Member GetType is NOT tested!

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