泛型反射获取特性值

泛型反射获取特性值，本文主要是讲述如何使用泛型以及反射来获取属性的特性值的。具体案例如下：

1、新建控制台项目 GenericReflectionGetsPropertyValues

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GenericReflectionGetsPropertyValues
{
class Program
{
static void Main(string[] args)
{

}
}
}

2、添加泛型反射获取类型的属性的特性值帮助类 CustomAttributeHelper

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GenericReflectionGetsPropertyValues
{
/// <summary>
/// 泛型反射获取类型的属性的特性值帮助类
/// </summary>
public static class CustomAttributeHelper
{
/// <summary>
/// 缓存字典
/// </summary>
public static readonly Dictionary<string, string> cacheKeyValuePairs = new Dictionary<string, string>();

/// <summary>
/// 泛型反射获取属性的特性值
/// </summary>
/// <typeparam name="T">泛型（特性）</typeparam>
/// <param name="type">获取属性的特性的类</param>
/// <param name="func">委托方法</param>
/// <param name="name">属性名称</param>
/// <returns>泛型反射获取属性的特性值</returns>
public static string GetCustomAttributeValue<T>(this Type type, Func<T, string> func, string name) where T : Attribute
{
if (func == null || string.IsNullOrEmpty(name))
{
return null;
}
return GetCustomAttribute(type, func, name);
}

/// <summary>
/// 获取属性的特性值
/// </summary>
/// <typeparam name="T">泛型（特性）</typeparam>
/// <param name="type">获取属性的特性的类</param>
/// <param name="func">委托方法</param>
/// <param name="name">属性名称</param>
/// <returns>反射获取属性的特性值</returns>
public static string GetCustomAttribute<T>(Type type, Func<T, string> func, string name) where T : Attribute
{
string key = GetKey(type, name);
string returnValue = null;
if (!cacheKeyValuePairs.ContainsKey(key))
{
CacheCustomAttribute(type, func, name);
if (cacheKeyValuePairs.ContainsKey(key))
{
returnValue = cacheKeyValuePairs[key];
}
}
else
{
returnValue = cacheKeyValuePairs[key];
}

return returnValue;

}

/// <summary>
/// 缓存属性的特性值
/// </summary>
/// <typeparam name="T">泛型（特性）</typeparam>
/// <param name="type">获取属性的特性的类</param>
/// <param name="func">委托方法</param>
/// <param name="name">属性名称</param>
public static void CacheCustomAttribute<T>(Type type, Func<T, string> func, string name) where T : Attribute
{
string key = GetKey(type, name);
string value = GetValue(type, func, name);
if (!string.IsNullOrEmpty(value))
{
if (!cacheKeyValuePairs.ContainsKey(key))
{
cacheKeyValuePairs[key] = value;
}
}
}

/// <summary>
/// 泛型反射获取特性值
/// </summary>
/// <typeparam name="T">特性类型</typeparam>
/// <param name="type">类型</param>
/// <param name="func">获取特性值的委托</param>
/// <param name="name">属性名</param>
public static string GetValue<T>(Type type, Func<T, string> func, string name) where T : Attribute
{
object customAttr = null;
if (string.IsNullOrEmpty(name))
{
customAttr = type.GetCustomAttributes(typeof(T), false).FirstOrDefault();
}
else
{
var item = type.GetProperty(name);
if (item != null)
{
customAttr = item.GetCustomAttributes(typeof(T), true).FirstOrDefault();
}
else
{
var field = type.GetField(name);
if (field != null)
{
customAttr = field.GetCustomAttributes(typeof(T), true).FirstOrDefault();
}
}
}

return customAttr == null ? null : func((T)customAttr);
}

/// <summary>
/// 获取类型中的属性名,作为字典的key
/// </summary>
/// <param name="type">类型</param>
/// <param name="name">名称</param>
/// <returns>类型中的属性名</returns>
public static string GetKey(Type type, string name)
{
if (string.IsNullOrEmpty(name))
{
return type.FullName;
}
return type.FullName + "." + name;
}
}
}

4、添加测试类 TestMyStudent

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GenericReflectionGetsPropertyValues
{
/// <summary>
/// 测试类
/// </summary>
[MyTestAtts("TestMyStudentN", "TestMyStudentP")]
public class TestMyStudent
{
[System.ComponentModel.Description("123")]
[MyTestAtts("IdN", "IdP")]
public int Id { get; set; }

[System.ComponentModel.Description("123")]
[MyTestAtts("NameN", "NameP")]
public string Name { get; set; }

[MyTestAtts("AgeN", "AgeP")]
public int Age { get; set; }
}
}

5、修改Program

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GenericReflectionGetsPropertyValues
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("开始");
var item = (typeof(TestMyStudent)).GetCustomAttributeValue<MyTestAttsAttribute>(x => x.MyName, nameof(TestMyStudent.Name));//调用测试泛型反射获取属性的特性值
Console.WriteLine($"反射的特性 Attribute的值: {item}");
var item2 = (typeof(TestMyStudent)).GetCustomAttributeValue<MyTestAttsAttribute>(x => x.MyName, nameof(TestMyStudent.Name));//测试缓存
Console.WriteLine($"反射的特性 Attribute的值: {item2}");
//GetValue<MyAttsAttribute>(typeof(TestMyStudent), x => x.MyName, nameof(TestMyStudent.Name));
Console.Read();
}

/// <summary>
/// 泛型反射获取特性值
/// </summary>
/// <typeparam name="T">特性类型</typeparam>
/// <param name="type">类型</param>
/// <param name="func">获取特性值的委托</param>
/// <param name="name">属性名</param>
public static void GetValue<T>(Type type, Func<T, string> func, string name) where T : Attribute
{
var item = type.GetProperty(name);
var cus = item.GetCustomAttributes(typeof(T), true).FirstOrDefault();
Console.WriteLine($"反射 {item.Name}的特性 Attribute的值: {func((T)cus)}");
}
}
}

6、测试运行结果：