C# 知识特性 Attribute

C#知识--获取特性 Attribute

特性提供功能强大的方法，用以将元数据或声明信息与代码（程序集、类型、方法、属性等）相关联。特性与程序实体关联后，可在运行时使用“反射”查询特性，获取特性集合方法是GetCustomAttributes();

根据约定，所有特性名称都以单词“Attribute”结束，以便将它们与“.NET Framework”中的其他项区分。但是，在代码中使用特性时，不需要指定 attribute 后缀。在声明特性类时要以“Attribute”结束，使用时省略“Attribute”单词。

下面是几种使用特性的方法，菜鸟只是多看了一下总结一下，大神可以绕过：

类、程序集上的特性采用方法：

         /// <summary>
         /// 获取特性值方法
         /// </summary>
         /// <param name="t"></param>
         /// <returns></returns>
         public static string OutputDescription(Type t)
         {
             var attributes = t.GetCustomAttributes();
             foreach (Attribute attribute in attributes)
             {
                 var attr = attribute as DescriptionAttribute;
                 if (attr != null)
                 {
                     return attr.Description;
                 }
             }
             return t.ToString();
         }

方法、属性采用扩展方法：

 /// <summary>
     /// 第一种获取特性值，适用只有单个特性
     /// </summary>
     public static class FingerGuessingGameTypeExtension
     {
         public static string GetEnumDescription(this FingerGuessingGameType enumType)
         {
             Type type = enumType.GetType();
             MemberInfo[] memberInfo = type.GetMember(enumType.ToString());
             if (memberInfo != null && memberInfo.Length > )
             {
                 object[] attrs = memberInfo[].GetCustomAttributes(typeof(DescriptionAttribute), false);
                 if (attrs != null && attrs.Length > )
                 {
                     return ((DescriptionAttribute)attrs[]).Description;
                 }
             }

             return enumType.ToString();
         }

         public static string GetEnumValue(this FingerGuessingGameType enumType)
         {
             Type type = enumType.GetType();
             MemberInfo[] memberInfo = type.GetMember(enumType.ToString());
             if (memberInfo != null && memberInfo.Length > )
             {
                 object[] attrs = memberInfo[].GetCustomAttributes(typeof(NameAttribute), false);
                 if (attrs != null && attrs.Length > )
                 {
                     return ((NameAttribute)attrs[]).Name;
                 }
             }

             return enumType.ToString();
         }
     }
     /// <summary>
     /// 第二种获取特性值，适用有多个特性
     /// </summary>
     public static class FingerExtension
     {
         private static Dictionary<Enum, ValueDescriptionPair> m_Dic=null;

         public static string GetDescription(this FingerGuessingGameType enumType)
         {
             if (m_Dic == null)
             {
                 Type type = enumType.GetType();
                 var allValues = Enum.GetValues(type).OfType<Enum>();
                 m_Dic = allValues.ToDictionary(p => p, p => GetDescriptionValue(type, p));
             }

             ValueDescriptionPair valueDescription;
             if (m_Dic.TryGetValue(enumType, out valueDescription))
             {
                 return valueDescription.Description;
             }
             return enumType.ToString();
         }

         public static string GetValue(this FingerGuessingGameType enumType)
         {
             if (m_Dic == null)
             {
                 Type type = enumType.GetType();
                 var allValues = Enum.GetValues(type).OfType<Enum>();
                 m_Dic = allValues.ToDictionary(p => p, p => GetDescriptionValue(type, p));
             }

             ValueDescriptionPair valueDescription;
             if (m_Dic.TryGetValue(enumType, out valueDescription))
             {
                 return valueDescription.Name;
             }
             return enumType.ToString();
         }

         private static ValueDescriptionPair GetDescriptionValue(Type type, Enum value)
         {
             var valueDescriptionPair=new ValueDescriptionPair();
             var enumName=Enum.GetName(type,value);
             var description=type.GetField(enumName)
                 .GetCustomAttributes(typeof (DescriptionAttribute), false)
                 .OfType<DescriptionAttribute>().FirstOrDefault();
             var enumValue = type.GetField(enumName)
                 .GetCustomAttributes(typeof(NameAttribute), false)
                 .OfType<NameAttribute>().FirstOrDefault();

             if (description != null)
             {
                 valueDescriptionPair.Description = description.Description;
             }
             if (enumValue != null)
             {
                 valueDescriptionPair.Name = enumValue.Name;
             }
             return valueDescriptionPair;
         }
     }

     public class NameAttribute:Attribute
     {
         public NameAttribute(string name)
         {
             Name = name;
         }
         public string Name { get; set; }
     }

     public class ValueDescriptionPair
     {
         //Description 特性
         public string Description { get; set; }
         //Value 特性
         public string Name { get; set; }
     }

序列化XML(XMLSerialize):

 using System;
 using System.IO;
 using System.Xml;
 using System.Xml.Serialization;

 public static class XMLSerializeExtension
 {
     public static string Serialize<T>(this T value)
     {
         var result = string.Empty;
         if (value == null)
         {
             return result;
         }
         try
         {
             var serializer = new XmlSerializer(typeof(T));
             var stringWriter = new StringWriter();
             using (var writer = XmlWriter.Create(stringWriter))
             {
                 serializer.Serialize(writer, value);
                 result = stringWriter.ToString();
             }
         }
         catch (Exception ex)
         {
             throw new Exception("An error occurred while XML serialize", ex);
         }
         return result;
     }

     public static T Deserialize<T>(this string value)
     {
         T retObj = default(T);
         if (string.IsNullOrWhiteSpace(value) == true)
         {
             return retObj;
         }
         try
         {
             using (var rdr = new StringReader(value))
             {
                 var serializer = new XmlSerializer(typeof(T));
                 retObj = (T)serializer.Deserialize(rdr);
             }
         }
         catch (Exception ex)
         {
             throw new Exception("An error occurred while XML Deserialize", ex);
         }
         return retObj;
     }
 }

反射调用方法(Reflection)

             Assembly assembly = Assembly.Load("ConsoleFileDemo");
             Type classType = assembly.GetType("ConsoleFileDemo.XmlOperator");
             ICase obj = Activator.CreateInstance(classType) as ICase;
             //获取默认方法并调用方法
             MethodInfo showMethod = classType.GetMethod("Show");
             showMethod.Invoke(assembly, new object[]{"parameter"});
             //获取无参方法并调用无参方法
             MethodInfo show1 = classType.GetMethod("Show1",new Type[]{});
             show1.Invoke(assembly,null);
             //获取指定参数的方法并调用  int，string
             MethodInfo show2 = classType.GetMethod("Show2", new Type[] {typeof (int)});
             show2.Invoke(assembly, new object[] {});

             MethodInfo show3 = classType.GetMethod("Show3", new Type[] { typeof(string) });
             show3.Invoke(assembly, new object[] {"name"});
             //获取指定私有方法并调用   string
             MethodInfo show4 = classType.GetMethod("Show4",
                 BindingFlags.Instance |BindingFlags.Public | BindingFlags.NonPublic,
                 null,new Type[]{typeof(string)}, null);
             show4.Invoke(assembly,new object[]{"name"});

             //创建单例模式,反射使用私有构造函数实例化单例
             Type typeSingle = assembly.GetType("ConsoleFileDemo.Singleton");
             object objectSingle = Activator.CreateInstance(typeSingle, true);