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POType.IsAssignableFrom() bug
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  1. POType.IsAssignableFrom() bug
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    copied!<p>I'd like to load some plugin (C# assembly) at runtime and use some of the classes implementing a certain interface inside each of them. So I wrote a base assemby (Interfaces.dll) in which I declare base interfaces:</p> <pre><code>namespace Interfaces { public interface IPlugin01 { string Name { get; } string Description { get; } void Calc1(); } public interface IPlugin02 { void Calc2(); } } </code></pre> <p>Then, in two different assemblies (Plugin01.dll and Plugin02.dll) I've implemented those interfaces using classes:</p> <pre><code>namespace Plugin01 { public class Class1 : Interfaces.IPlugin01,Interfaces.IPlugin02 { public string Name { get { return "Plugin01.Class1"; } } public string Description { get { return "Plugin01.Class1 description"; } } public void Calc1() { Console.WriteLine("sono Plugin01.Class1 Calc1()"); } public void Calc2() { Console.WriteLine("sono Plugin01.Class1 Calc2()"); } } public class Class2 : Interfaces.IPlugin01 { public string Name { get { return "Plugin01.Class2"; } } public string Description { get { return "Plugin01.Class2 description"; } } public void Calc1() { Console.WriteLine("sono Plugin01.Class2 Calc1()"); } } } </code></pre> <p>and</p> <pre><code>namespace Plugin02 { public class Class1 : Interfaces.IPlugin01 { public string Name { get { return "Plugin02.Class1"; } } public string Description { get { return "Plugin02.Class1 description"; } } public void Calc1() { Console.WriteLine("sono Plugin02.Class1 Calc1()"); } } public class Class2 : Interfaces.IPlugin02 { public void Calc2() { Console.WriteLine("sono Plugin02.Class2 Calc2()"); } } } </code></pre> <p>Finally the test console app:</p> <pre><code>//#define LIST1 #define LIST2 using System; using System.Collections.Generic; using System.Reflection; using System.IO; using System.Diagnostics; namespace Test { class Program { static void Main(string[] args) { #if LIST1 List&lt;Interfaces.IPlugin01&gt; list1 = GetFilePlugins&lt;Interfaces.IPlugin01&gt;(@".\Plugins\Plugin01.dll"); #else List&lt;Interfaces.IPlugin01&gt; list1 = new List&lt;Interfaces.IPlugin01&gt;(); #endif #if LIST2 List&lt;Interfaces.IPlugin01&gt; list2 = GetFilePlugins&lt;Interfaces.IPlugin01&gt;(@".\Plugins\Plugin02.dll"); #else List&lt;Interfaces.IPlugin01&gt; list2 = new List&lt;Interfaces.IPlugin01&gt;(); #endif /// ------------------------------------------------------------------------------ /// If I don't load one of the assembly using LIST1 or LIST2 /// GetDirectoryPlugins returns an empty list. /// The bug (is a bug or my mistake?) is inside GetFilePlugins: /// typeT.IsAssignableFrom(type) returns FALSE even if interface is implemented !!! /// Using LIST1 or LIST2 before using GetDirectoryPlugins makes /// typeT.IsAssignableFrom(type) return TRUE as expected !!! /// I'm going crazy over this.... /// ------------------------------------------------------------------------------ List&lt;Interfaces.IPlugin01&gt; listtot = GetDirectoryPlugins&lt;Interfaces.IPlugin01&gt;(@".\Plugins\"); #if LIST1 Console.WriteLine("--- 001 ---"); foreach(Interfaces.IPlugin01 plugin in list1) plugin.Calc1(); #endif #if LIST2 Console.WriteLine("--- 002 ---"); foreach (Interfaces.IPlugin01 plugin in list2) plugin.Calc1(); #endif Console.WriteLine("--- TOT ---"); foreach (Interfaces.IPlugin01 plugin in listtot) plugin.Calc1(); Console.ReadLine(); } public static List&lt;T&gt; GetFilePlugins&lt;T&gt;(string filename) { List&lt;T&gt; ret = new List&lt;T&gt;(); if (File.Exists(filename)) { Type typeT = typeof(T); Assembly ass = Assembly.LoadFrom(filename); foreach (Type type in ass.GetTypes()) { if (!type.IsClass || type.IsNotPublic) continue; Debug.Print("{0} &lt;- {1}", typeT.IsAssignableFrom(type), type); if (typeT.IsAssignableFrom(type)) { T plugin = (T)Activator.CreateInstance(type); ret.Add(plugin); } } } return ret; } public static List&lt;T&gt; GetDirectoryPlugins&lt;T&gt;(string dirname) { List&lt;T&gt; ret = new List&lt;T&gt;(); string[] dlls = Directory.GetFiles(dirname, "*.dll"); foreach (string dll in dlls) { List&lt;T&gt; dll_plugins = GetFilePlugins&lt;T&gt;(Path.GetFullPath(dll)); ret.AddRange(dll_plugins); } return ret; } } } </code></pre> <p>As written in comment, if I leave both rows <strong><em>#define LIST1</em></strong> and <strong><em>#define LIST2</em></strong> commented, IsAssignableFrom() returns false even if my class implements desired interface. Why?</p>
 

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