could not load dll or one of its dependency

Question

a. My C# program will load a dll (which is dynamic), for now let's take a.dll (similarly my program will load more dll like b.dll, c.dll, etc....).

b. My program will invoke a method "Onstart" inside a.dll (it's constant for all the dll).

I am able to achieve the above 2 cases by reflection mechanism.

The problem is

a. If my a.dll have any reference say xx.dll or yy.dll, then when I try to Invoke

OnStart method of a.dll from my program. I am getting "could not load dll or one of its dependency". See the code snippet

Assembly assm = Assembly.LoadFrom(@"C:\Balaji\Test\a.dll");

foreach (Type tp in assm.GetTypes())

{

  if (tp.IsClass)

  {
    MethodInfo mi = tp.GetMethod("OnStart");

    if (mi != null)
   {
      object obj = Activator.CreateInstance(tp);
      mi.Invoke(obj,null);
      break;
    }
   }
 }

typically i am getting error on the line "object obj = Activator.CreateInstance(tp);" this is because a.dll has reference of xx.dll, but in my program i don't have the reference of xx.dll. Also, I cannot have the reference of xx.dll in my program because a.dll is a external assembly and can have any reference on it's own.

Kinldy help!!!

Answer 1

Perhaps the second DLL reference isn't available to your application?

Make sure the second DLL is in the same directory as the first DLL or that the application is configured to look in a directory that does have the second DLL.

Answer 2

I think, it needs more explanation. Let me explain....

a. My C# program will load a dll (which is dynamic), for now let's take a.dll (similarly more dll like b.dll, c.dll, etc....). b. My program will invoke a method "Onstart" (it's constant for all the dll) inside a.dll.

I am able to achieve the above 2 cases by reflection mechanism.

The problem is

a. If my a.dll have any reference say xx.dll or yy.dll, then when I try to Invoke

OnStart method of a.dll from my progra. I am getting "could not load dll or one of its dependency".

See the code snippet

Assembly assm = Assembly.LoadFrom(@"C:\Balaji\Test\a.dll"); foreach (Type tp in assm.GetTypes()) { if (tp.IsClass) { MethodInfo mi = tp.GetMethod("OnStart"); if (mi != null) { object obj = Activator.CreateInstance(tp); mi.Invoke(obj,null); break; } } }

typically i am getting error on the line "object obj = Activator.CreateInstance(tp);" this is because a.dll has reference of xx.dll, but I cannot have the same. Also, I cannot have the reference of xx.dll in my program, because a.dll is dynamic and can have any reference on it's own.

Answer 3

I think you can not do anything other than adding all references which are used . ps : usually an external assembly should be complete for use (or the package will contain all needed assemblies so you can add them)

Answer 4

Have a look at this: http://bytes.com/topic/c-sharp/answers/232691-how-dynamically-load-assembly-w-dependencies. Basically, in the AssemblyResolve event, you need to load the referenced assemblies manually.

private Assembly AssemblyResolveHandler(object sender,ResolveEventArgs e)
{
    try
    {
        string[] assemblyDetail = e.Name.Split(',');
        string assemblyBasePath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
        Assembly assembly = Assembly.LoadFrom(assemblyBasePath + @"\" + assemblyDetail[0] + ".dll");
        return assembly;
    }
    catch (Exception ex)
    {
        throw new ApplicationException("Failed resolving assembly", ex);
    }
}

Not the best code, but should give you a general idea, I hope.

I do, however, agree that plugin-dlls should be packaged for complete, dependancy-less use. If they are allowed to load assemblies you don't have control over, then who knows what might happen.