C#: Could not load file or assembly

Exception:

Could not load file or assembly 'DllFileName, Version=1.0.0.0, Culture=neutral, PublicKeyToken=5cadd04e079758c3' or one of its dependencies. The system cannot find the file specified.

最近在研究動態讀取非當前EXE目錄的DLL文件的方法。

Reflection, Activator.CreateInstance,或者AppDomain啥的。

當只讀取單個Dll的時候沒啥問題，但是當這個Dll以來和它同一個文件夾的dll時，就會報錯。

搜了很久，終於搜到篇靠譜的文章。

http://theraneman.blogspot.com/2010/04/creating-instance-of-type-outside.html

文章是2010年的，10年過去了，呵呵。。。

大致解決方法代碼如下，直接COPY過來留個念，慢慢啃。

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1. 一般操作，會導致報錯

Assembly assembly = Assembly.LoadFrom(C:\Sample\Sample.dll);
Type appType = assembly.GetType(MyType);
object objClassInstance = Activator.CreateInstance(appType);

2. 解決方案一

有點過的方案，哈哈，

使用這個方法，不能直接實例化你需要的函數，而必須實例化一個繼承了MarshalByRefObject的函數，

入下面代碼中的SampleProxy

Assembly assembly = Assembly.LoadFrom(@"C:\Sample\Sample.dll");
AppDomainSetup setup = new AppDomainSetup();
setup.ApplicationBase = @"C:\Sample\";
AppDomain appDomain = AppDomain.CreateDomain("AppHostDomain", null, setup);
object obj = appDomain.CreateInstanceFromAndUnwrap(@"C:\Sample\Sample.dll", "SampleProxy");

3.解決方案二

被原作者成為冗余啰嗦的方案，不過在我看來挺好的。

該方案將循環遞歸加載所依賴的DLL

Assembly assembly = Assembly.LoadFrom(@"C:\Sample\Sample.dll"); 
AssemblyName[] arr = assembly.GetReferencedAssemblies();                
LoadAssembly(arr);


private void LoadAssembly(AssemblyName[] arr)
{
    Assembly[] loadedAssemblies = AppDomain.CurrentDomain.GetAssemblies();
    List<string> names = new List<string>();
    foreach (Assembly assem in loadedAssemblies)
    {
        names.Add(assem.FullName);
    }

    foreach (AssemblyName aname in arr)
    {
        if (!names.Contains(aname.FullName))
        {
            try
            {
                Assembly loadedAssembly = Assembly.LoadFrom(@"C:\Sample\" + aname.Name + ".dll");
                AssemblyName[] referencedAssemblies = loadedAssembly.GetReferencedAssemblies();
                LoadAssembly(referencedAssemblies);
            }
            catch (Exception ex)
            {
                continue;
            }
        }
    }
}

3. 解決方案三

定於當前AppDomain的一個事件，就是當需要哪個Assembly而又找不到時，就會觸發。

Assembly assembly = Assembly.LoadFrom(@"C:\Sample\Sample.dll");
AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(CurrentDomain_AssemblyResolve);
object obj = Activator.CreateInstanceFrom(@"C:\Sample\Sample.dll", "MyType");

Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
{
    string path = @"C:\Sample\Sample.dll";
    string test = path.Substring(0,path.LastIndexOf(@"\"));
    string[] arr = args.Name.Split(',');
    string assemblyName = args.Name.Substring(0, args.Name.IndexOf(",")) + ".dll";
    string newPath = System.IO.Path.Combine(test, assemblyName);
    return Assembly.LoadFrom(newPath);
}