Invoke extension method using reflection

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I have a List of object because I will have diferent kind of classes (ex: Class1, Class2) and I don't know what the list will contains.

Then I have create for each class an extension method
(ex: public static Save(this Class1 c1) {})

As I have created an extension method for the list
(ex: public static Save(this List<object> lstObj) {})

The scenario is after filling the list with the object I call the extended Save() method of the list. In this method I need to loop through all the object and for foreach object I need to call the extented Save() method for it.

Any idea?

Posted 28-Sep-10 20:44pm

ziadb86

Updated 28-Sep-10 21:14pm

Sandeep Mewara

v2

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Fredrik Bornander · Answer 1 · 2010-09-28T21:57:00

I would recommend trying to solve this by having the Class1 and Class2 implement some sort of ISaveable interface instead, but if that can't be done then here's two different solutions.

The first one tries to find any matching extension method in the calling assembly, and the second one is slightly more efficient but forces you to specify the type owning the extension methods:

C#

public static class Extensions
{
    public static void Save(this A instance)
    {
        Console.WriteLine("Saving A");
    }
    public static void Save(this B instance)
    {
        Console.WriteLine("Saving B");
    }
    private static bool IsMethodOk(MethodInfo method, object obj)
    {
        return
            method.IsStatic
            &&
            method.GetParameters().Count() == 1
            &&
            method.GetParameters()[0].ParameterType == obj.GetType();
    }
    public static void Save1(this IList<object> list)
    {
        foreach (object obj in list)
        {
            foreach (Type type in Assembly.GetCallingAssembly().GetTypes())
            {
                bool hasSaved = false;
                foreach (MethodInfo method in type.GetMethods())
                {
                    if (IsMethodOk(method, obj))
                    {
                        method.Invoke(null, new[] { obj });
                        hasSaved = true;
                        break;
                    }
                }
                if (hasSaved)
                    break;
            }
        }
    }
    public static void Save2(this IList<object> list, Type extensionClass)
    {
        foreach (object obj in list)
        {
            foreach (MethodInfo method in extensionClass.GetMethods())
            {
                if (IsMethodOk(method, obj))
                {
                    method.Invoke(null, new[] { obj });
                    break;
                }
            }
        }
    }
}

Hope this helps,
Fredrik

ziadb86 · Answer 2 · 2010-09-29T00:21:00

I have resolved my problem using the below code...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Namespace1;
using System.Reflection;
using System.Data.Linq;

namespace Namespace2
{
    public static class Extensions
    {
        public static void Save(this IList<object> list)
        {
            if (list.Count > 0)
            {
                Assembly thisAssembly = Assembly.GetExecutingAssembly();//Assembly containin the extension method
                int objCount = list.Count;
                object currentObj;
                Type currentType = list[0].GetType();
                for (int i = 0; i < objCount; i++)
                {
                    currentObj = list[i];

                    //Since the query will return an IEnumarable object so I must use the foreach loop
                    //although I only have one extension method
                    foreach (MethodInfo method in GetExtensionMethods(thisAssembly, currentType))
                    {
                        method.Invoke(null, new object[] { currentObj });
                    }
                }
            }
        }

        static IEnumerable<MethodInfo> GetExtensionMethods(Assembly assembly, Type extendedType)
        {
            var query = from type in assembly.GetTypes()
                        where !type.IsGenericType && !type.IsNested
                        from method in type.GetMethods(BindingFlags.Static
                            | BindingFlags.Public | BindingFlags.NonPublic)
                        where method.IsDefined(typeof(System.Runtime.CompilerServices.ExtensionAttribute), false)
                        where method.GetParameters()[0].ParameterType == extendedType
                        select method;
            return query;
        }

        public static void Save(this Class1 c1)
        {
            Console.WriteLine("Saving C1");
        }
    }   
}

Invoke extension method using reflection

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