C# dotnet core 中同一属性的多个方法的自定义属性声明

Question

正如我在其他问题中提到的 , and based on the answer given by @Abdul Rahman 我能够 call/reject 使用以下代码调用属性下的函数：

using System;
using System.Linq;    // for using Where
using System.Reflection;

namespace attribute
{
public class Program
{
    public static int Main(string[] args)
    { 
        var customAttributes = (MyCustomAttribute[])((typeof(Foo).GetTypeInfo())
            .DeclaredMethods.Where(x => x.Name == "fn")  // my question about this
            .FirstOrDefault())
            .GetCustomAttributes(typeof(MyCustomAttribute), true);
        if (customAttributes.Length > 0)
        {
            var myAttribute = customAttributes[0];
            string value = myAttribute.SomeProperty;
            if (value == "bar")
                Foo.fn();
            else
                Console.WriteLine("The attribute parameter is not as required");
        }
        return 0;
    }
  }
}

到目前为止，Attribute 和 Foo 类很简单，因为我正处于学习阶段：

[AttributeUsage(AttributeTargets.All)]
public class MyCustomAttribute : Attribute
{
    public string SomeProperty { get; set; }
}


public class Foo
{
    [MyCustom(SomeProperty = "bar")]
    internal static void fn()
    {
        Console.WriteLine("a function in a class");
    }

    [MyCustom(SomeProperty = "bar")]
    internal static void fn2()
    {
        Console.WriteLine("another function in the same class");
    }
}

public class Foo2
{
    [MyCustom(SomeProperty = "bar")]
    internal static void fn2()
    {
        Console.WriteLine("another function in a nother class");
    }
}

我的问题是关于 .DeclaredMethods.Where(x => x.Name == "fn") 我是否需要为我添加的每个功能重复相同的操作，或者有一个简单的扩展可以为我做这个，我的目标就是这样，我需要检查属性参数，如果和我的输入匹配，我需要启动属性下的函数，如果不匹配，函数不会运行。谢谢

更新将示例代码添加到 ideone.com 以便于检查 http://ideone.com/E9uL6r

Answer 1

可以准备f.e。您需要的函数名称集合：

var targetFns = new HashSet<string>(new[] { "fn", "fn2","fn3" });
...
.DeclaredMethods.Where(x => targetFns.Contains(x.Name));

如果 targetFns 中的项目数量较少，您可以只使用数组而不是 HashSet。

所以，总结一下：

var method = (typeof(Foo).GetTypeInfo())
             .DeclaredMethods.Where(x => targetFns.Contains(x.Name)).FirstOrDefault();

if (method == null) return;

var customAttributes = (MyCustomAttribute[])method.GetCustomAttributes(
                                                      typeof(MyCustomAttribute), true);
...
if (value == "bar")
   method.Invoke(null, null);

Answer 2

我会四处做一个像这样的通用方法

public static void CallMethod<T>(string methodName, string value)
{
    var method = typeof(T).GetMethod(methodName, BindingFlags.DeclaredOnly | BindingFlags.Static | BindingFlags.NonPublic);
    if (method == null)
    {
        Console.WriteLine("The method not found");

        return;
    }

    foreach (var myAttribute in method.GetCustomAttributes<MyCustomAttribute>())       
    {
        if (myAttribute.SomeProperty == value)
        {
            method.Invoke(null, null);
        }
        else
        {
            Console.WriteLine("The attribute parameter is not as required");
        }
    }
}

你可以调用哪个

CallMethod<Foo>("fn", "bar");

Answer 3

我假设您的方法是静态的。所以他们不需要对象实例。

 static  void ExecuteFunction(Type T,string functionName, string Value)
        {
            MethodInfo m = ((T.GetTypeInfo()).DeclaredMethods.Where(x => x.Name == functionName).FirstOrDefault());
            //var customAttributes = (MyCustomAttribute[])((T.GetTypeInfo()).DeclaredMethods.Where(x => x.Name == functionName).FirstOrDefault()).GetCustomAttributes(typeof(MyCustomAttribute), true);
            var customAttributes = (MyCustomAttribute[])(m.GetCustomAttributes(typeof(MyCustomAttribute), true));

            if (customAttributes.Length > 0)
            {
                var myAttribute = customAttributes[0];
                string value = myAttribute.SomeProperty;
                // TODO: Do something with the value
                Console.WriteLine(value);
                if (value == Value)
                {
                    m.Invoke(null, null);
                }
                else
                    Console.WriteLine("Unauthorized");
            }

        }

& 执行为

 ExecuteFunction(typeof(Foo), "fn", "bar");

编辑： 根据您的错误更新解决方案：您正在检查字符串。您应该根据字符串获取 class，然后检查其中的方法。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Reflection;

namespace ConsoleApp1Core
{
    [AttributeUsage(AttributeTargets.All)]
    public class MyCustomAttribute : Attribute
    {
        public string SomeProperty { get; set; }
    }


    public class Foo
    {
        [MyCustom(SomeProperty = "bar")]
        internal static void fn()
        {
            Console.WriteLine("a function in a class");
        }

        [MyCustom(SomeProperty = "bar")]
        internal static void fn2()
        {
            Console.WriteLine("another function in the same class");
        }
    }

    public class Foo2
    {
        [MyCustom(SomeProperty = "bar")]
        internal static void fn2()
        {
            Console.WriteLine("another function in a nother class");
        }
    }


    public class Program
    {
        public static int Main(string[] args)
        {
            var targetClasses = new HashSet<string>(new[] { "ConsoleApp1Core.Foo", "ConsoleApp1Core.Foo2" });
            var targetFns = new HashSet<string>(new[] { "fn", "fn2", "fn3" });
            var j = 0;
            foreach (var target in targetClasses)
            {
                Console.WriteLine("_class round {0}", j++);
                var i = 0;
                foreach (var fn in targetFns)
                {
                    Console.WriteLine("fn round {0}", i++);
                    Type t = Type.GetType(target);
                    var method = (t.GetTypeInfo()) // (typeof(Foo).GetTypeInfo())
                      .DeclaredMethods.Where(x => x.Name == fn).FirstOrDefault();
                    if (method != null) //return 0;
                    {
                        var customAttributes = (MyCustomAttribute[])method
                                               .GetCustomAttributes(typeof(MyCustomAttribute), true);
                        if (customAttributes.Length > 0)
                        {
                            var myAttribute = customAttributes[0];
                            string value = myAttribute.SomeProperty;
                            if (value == "bar")
                                method.Invoke(null, null);
                            //  Foo.fn();;
                            else
                                Console.WriteLine("The attribute parameter is not as required");
                        }
                    }
                    else
                    {
                        Console.WriteLine("Method not found");
                    }

                }
            }
            return 0;
        }
    }
}

C# dotnet core 中同一属性的多个方法的自定义属性声明

Custom attributes declaration of multiple methods for the same attribute in C# dotnet core

c#

extension-methods

custom-attributes

.net-core