Question on System.Reflection namespace

Question

I am coding support for plug-ins and I am doing it via an interface I define from which all classes intended as plugins have to implement. The question I have right now is whether or not this code works... Basically what I do here is load an assembly from a file get the types contained and create new instances of NodeRenderer for those that implement I_HwRenderer. The code for the constructor in the NodeRenderer uses Activator.CreateInstance for the given type and then attempts to cast it to the I_HwRenderer interface. The places where I have my doubts are... 1. Will comparing to that static variable HwR_InterfaceType (bottom of the code block) return true when the type does implement I_HwRenderer? 2. Am I searching the assembly in the right way? 3. Am I allowed to cast the object returned by Activator.CreateInstance to the implemented interface? Thanks in advance. I_HwRenderer instance; public NodeRenderer(Type t) { instance = (I_HwRenderer)(Activator.CreateInstance(t)); } public static NodeRenderer[] FromDll(string dllPath) { ArrayList foundRenderers = new ArrayList(); Assembly nrAssembly = Assembly.LoadFile(dllPath); Type[] types = nrAssembly.GetTypes(); //search for classes in assembly that implement I_HwRenderer for (int i=0; i<types.Length; i++) { if (typeImplementsHwRenderer(types[i])) { //Create NodeRenderers for compatible types. foundRenderers.Add(new NodeRenderer(types[i])); } } //return NodeRenderers NodeRenderer[] f = new NodeRenderer[foundRenderers.Count]; foundRenderers.CopyTo(f); return f; } private static bool typeImplementsHwRenderer(Type t) { if (HwR_InterfaceType == null) HwR_InterfaceType = Type.GetType(ItemTreeRenderer.I_HwRenderer); Type[] interfaces = t.GetInterfaces(); for (int i=0; i<interfaces.Length; i++) { if (interfaces[i].Equals(HwR_InterfaceType)) return true; } //if interfaces not found return false; } public static Type HwR_InterfaceType = Type.GetType(ItemTreeRenderer.I_HwRenderer);

Mykonine · Answer

Ok another question... to invoke a method through Reflection... so I use public NodeRenderer(Type t) { instance = Activator.CreateInstance(t); } later to invoke a method for which I know its signature and that the class I instantiated has that method would this work? The signature of the method I'm trying to invoke is public Bitmap getPreview (Size Size string) ItemTreeWriter.exportToString returns an object of type string. public Bitmap getPreview(Size currentScreenSize Size thumbnailSize ItemTreeRootNode sampleRootNode) { object[] os = new object[3]; os[0] = currentScreenSize; os[1] = thumbnailSize; os[2] = ItemTreeWriter.exportToString(sampleRootNode); return (Bitmap)(instance.GetType().InvokeMember(getPreview BindingFlags.Public | BindingFlags.InvokeMethod | BindingFlags.Instance null instance os)); } Once again thanks in advance for taking the time to tolerate my complete ignorance.

bilnaad · Answer

1. Will comparing to that static variable HwR_InterfaceType (bottom of the code block) return true when the type does implement I_HwRenderer? I guess :) 2. Am I searching the assembly in the right way? Maybe in the method typeImplementsHwRenderer you can replace the current code with this. current: interfaces[i].Equals(HwR_InterfaceType) replace: interfaces[i] is Hwr_InterfaceType 3. Am I allowed to cast the object returned by Activator.CreateInstance to the implemented interface? If the interface is truly implemented then it's absolutly valid.