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        在C#中，特性（Attribute）是一种用于向代码元素（如类、方法、属性等）添加元数据的机制。特性本身不会直接影响代码的执行，但它们可以提供额外的信息，这些信息可以在运行时通过反射（Reflection）来读取和使用。

用法：

一、描述

using System;[AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
public class DescriptionAttribute : Attribute
{public string Description { get; set; }public DescriptionAttribute(string description){Description = description;}
}
[DescriptionAttribute("描述特性") ]//Attribute允许省略
public class Test
{}public class Program
{public static void Main(string[] args){Type type= typeof(Test);object[] attributes = type.GetCustomAttributes(typeof(DescriptionAttribute), false);if(attributes.Length > 0){DescriptionAttribute descriptionAttribute= (DescriptionAttribute)attributes[0];Console.WriteLine(descriptionAttribute.Description);//会输出文字：描述特性}Console.Read();}
}

二、标记过时方法

using System;public class Program
{[Obsolete("该方法已过时")]public static void ObsoleteMethod(){}public static void Main(string[] args){ObsoleteMethod();Console.Read();}
}

三、控制序列化

using System;
using System.IO;
using System.Xml.Serialization;[Serializable]
public class Test
{public string field1 = "";[XmlIgnore]public string field2 = "";
}public class Program
{public static void Main(string[] args){Test test;Test testDeserializer;XmlSerializer serializer;StringWriter writer;StringReader reader;test = new Test();test.field1 = "field1";test.field2 = "field2";serializer = new XmlSerializer(typeof(Test));writer = new StringWriter(); serializer.Serialize(writer, test);Console.WriteLine($"XML序列化结果：\n{writer}");reader = new StringReader(writer.ToString());testDeserializer = (Test)serializer.Deserialize(reader);Console.WriteLine($"XML反序列化结果：\nfield1:[{testDeserializer.field1}].field2:[{testDeserializer.field2}]" );Console.Read();}
}

四、自定义验证

using System;
using System.Reflection;[AttributeUsage(AttributeTargets.Property)]
public class RangeAttribute : Attribute
{public int Min { get; }public int Max { get; } public RangeAttribute(int min, int max){Min = min;Max = max;}   
}public class Test
{[Range(114,514)]public int Property1 {  get; set; }public  Test(int property1){Property1 = property1;}public bool ValidateProperty1(){MemberInfo property1 = typeof(Test).GetProperty("Property1");RangeAttribute rangeAttribute = (RangeAttribute)Attribute.GetCustomAttribute(property1, typeof(RangeAttribute));if (rangeAttribute != null){return Property1 >= rangeAttribute.Min && Property1 <= rangeAttribute.Max;}else{return true;}}
}public class Program
{public static void Main(string[] args){Test test1 = new Test(123);Test test2 = new Test(999);Console.WriteLine(test1.ValidateProperty1());Console.WriteLine(test2.ValidateProperty1());Console.Read();}
}

五、条件编译

#define Debug
using System;
using System.Diagnostics;public class Program
{[Conditional("Debug")]public static void Log(string message){Console.WriteLine(message);}public static void Main(string[] args){Log("Debug已定义");Console.Read();}
}

注释掉#define Debug代码，则执行不会输出“Debug已定义”。