卸载程序集

卸载程序集

2015-04-16

 

Assembly没有Unload方法，那么程序如何在运行状态下卸载程序集呢？

可以用AppDomain.Unload方法。

想法一 （失败）：

1. create new Domain
2. load assembly in new domain
3. unload the new Domain

代码如下：

using System;

using System.Reflection;

namespace UnloadAssembly
{
    class Program
    {
        static void Main(string[] args)
        {
            string file1 = @"C:\code\UnloadAssembly\Assembly1\bin\Debug\Assembly1.dll";
            AppDomain appD = AppDomain.CreateDomain("#D1"); 
            AssemblyName myAssemblyName1 = AssemblyName.GetAssemblyName(file1);
            System.IO.File.Copy(file1, GetDestinateFile(file1), true);
            appD.Load(myAssemblyName1);
            string dName = appD.FriendlyName;
            AppDomain.Unload(appD);
        }

        public static string GetDestinateFile(string file)
        {
            return Environment.CurrentDirectory + @"\" + new System.IO.FileInfo(file).Name;
        }
    }
}

图1 想法一

想法二 ^[1]（成功）：

Create a class say class "B" derived by MarshalByRefObject

• Write a method LoadAssembly({AssemblyPath}) in class "B". This function will only load that assembly and return void.
• Write another method ExecuteMethod({ClassName, MethodName, Params}) in class "B" . This function execute the method (name passed in the parameter) of the loaded assembly.

Create a new class say class "A". This will be our main class from where we will start and execute the code.

• write a main method in class "A" which will load class "B" in the new appdomain, and then call class B methods to load the assembly by passing the loadassembly method by passing assembly path and then by calling ExecuteMethod by passing method name and parameters.

 代码如下：

using System;
using System.Reflection;

namespace UnloadAssembly
{
    class Program
    {
        static void Main(string[] args)
        {
            string file1 = @"C:\code\UnloadAssembly\Assembly1\bin\Debug\Assembly1.dll";
            //Creating a new appdomain 
            AppDomainSetup setup = AppDomain.CurrentDomain.SetupInformation;
            //Create an instance of loader class in new appdomain 
            AppDomain newDomain = AppDomain.CreateDomain("newDomain", AppDomain.CurrentDomain.Evidence, setup);

            System.Runtime.Remoting.ObjectHandle obj = newDomain.CreateInstance(typeof(LoadMyAssembly).Assembly.FullName, typeof(LoadMyAssembly).FullName);

            //As the object we are creating is from another appdomain hence we will get that object in wrapped format and hence in next step we have unwrappped it 
            LoadMyAssembly loader = (LoadMyAssembly)obj.Unwrap();

            //Call loadassembly method so that the assembly will be loaded into the new appdomain amd the object will also remain in new appdomain only. 
            loader.LoadAssembly(file1);

            //Call exceuteMethod and pass the name of the method from assembly and the parameters. 
            loader.ExecuteStaticMethod("MyClass", "MyMethod", new object[] { 1 });

            //After the method has been executed call unload method of the appdomain. 
            AppDomain.Unload(newDomain); 
        }

        public sealed class LoadMyAssembly : MarshalByRefObject
        {
            private Assembly _assembly;
            System.Type MyType = null;
            object inst = null;
            public override object InitializeLifetimeService()
            {
                return null;
            }

            public void LoadAssembly(string path)
            {
                _assembly = Assembly.Load(AssemblyName.GetAssemblyName(path));
            }

            public object ExecuteStaticMethod(string className, string methodName, params object[] parameters)
            {
                foreach (System.Type type in _assembly.GetTypes())
                {
                    if (String.Compare(type.Name, className, true) == 0)
                    {
                        MyType = type;
                        inst = _assembly.CreateInstance(type.FullName);

                        break;
                    }
                }
                MethodInfo MyMethod = MyType.GetMethod(methodName, new Type[] { typeof(int) });
                MyMethod.Invoke(inst, BindingFlags.InvokeMethod, null, parameters, null);
                return null;
            }
        }

        public static string GetDestinateFile(string file)
        {
            return Environment.CurrentDirectory + @"\" + new System.IO.FileInfo(file).Name;
        }
    }
}

被加载的assembly代码如下：

    public class MyClass
    {
        public string MyMethod(int i)
        {
            return (i * 2).ToString();
        }
    }

参考

[1] How to Unload an Assembly Loaded Dynamically Using Reflection