List, load and instantiate unknown classes in App_Code at run-time

Answer 1

It strikes me as a bad idea to actually upload into your App_Code folder. I'd use a separate folder which ASP.NET doesn't know anything about. That way you won't get the framework trying to automatically compile code for you.

You can easily compile and run code on the fly with CSharpCodeProvider - see my source code for Snippy for an example.

I hope this is only for internal (and authenticated) use though - I wouldn't recommend letting untrusted users execute their code on your web server. You can make it all slightly safer by running the code which very much reduced permissions, but you still risk the code tight-looping etc.

EDIT: In response to your updated question, you just need to provide the appropriate assembly to reference, containing IModule. See the CompilerParameters.ReferencedAssembles property.

Answer 2

Assembly assembly = Assembly.Load(assemblyName);

IModule instance = assembly.CreateInstance(typeName) as IModule;

You could also use the Activatore.CreateInstance() method to create an instance without explicitly refering to the assembly.

Answer 3

you can do it using reflection and here is a very simple method which will return you the instance of the module name [class name] you pass to the function

Public Shared Function GetDALInstance(ByVal moduleClassName As String) As IModule
        Dim className As String
        dim path as string = <<NamespacePath>>  
        className = Path + moduleClassName
        Return Assembly.Load(Path).CreateInstance(className)
    End Function

the above method is in vb.net you can simply convert this to c#

Answer 4

I decided that classes which loads at run-time has to implement a given interface and that the name of the class has to be the same as the filename.

The folder the classes are uploaded to and compiled to is irrelevant.


Loading a compiled class (.dll) and instantiating it:

return (IInterfaceClassesMustImplement)Assembly
/* continued --> */ .LoadFile("c:\...\SomeClass.dll")
/* continued --> */ .CreateInstance("SomeClass");

Compile a class:

internal static class Compiler
{
    internal static void AssemblyFromFile(
        String classFilePath,
        String assemblyFilePath,
        String[] referencedAssemblies
    )
    {
        var cp = new CompilerParameters { OutputAssembly = assemblyFilePath };

        foreach (String ra in referencedAssemblies)
        {
            cp.ReferencedAssemblies.Add(ra);
        }

        CompilerResults cr = CodeDomProvider.CreateProvider("CSharp")
        /* continued --> */ .CompileAssemblyFromFile(cp, classFilePath);

        if (cr.Errors.Count > 0) // throw new Exception();
    }
}