Question

I want to load an assembly (its name is stored in a string), use reflection to check if it has a method called “CustomType MyMethod(byte[] a, int b)” and call it or throw an exception otherwise. I guess I should do something like this, but would appreciate if someone could offer same advice on how best to do it:

Assembly asm = Assembly.Load("myAssembly"); /* 1. does it matter if write myAssembly or myAssembly.dll? */

Type t = asm.GetType("myAssembly.ClassName");

// specify parameters
byte[] a = GetParamA();
int b = GetParamB();

object[] params = new object[2];
params[0] = a;
params[1] = b;

/* 2. invoke method MyMethod() which returns object "CustomType" - how do I check if it exists? */
/* 3. what's the meaning of 4th parameter (t in this case); MSDN says this is "the Object on which to invoke the specified member", but isn't this already accounted for by using t.InvokeMember()? */
CustomType result = t.InvokeMember("MyMethod", BindingFlags.InvokeMethod, null, t, params);

Is this good enough, or are there better/faster/shorter ways? What about constructors, given that these methods are not static – can they simply be ignored?

When invoking void Methods(), is it ok to just write t.InvokeMember(…) or should you always do Object obj = t.InvokeMember(…)?

Thanks in advance.

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EDIT
I have provided a working example as a separate answer below.

Answer 1

use reflection to check if it has a method called “CustomType MyMethod(byte[] a, int b)” and call it or throw an exception otherwise

Your current code isn’t fulfilling that requirement. But you can pretty easily with something like this:

var methodInfo = t.GetMethod("MyMethod", new Type[] { typeof(byte[]), typeof(int) });
if (methodInfo == null) // the method doesn't exist
{
    // throw some exception
}

var o = Activator.CreateInstance(t);

var result = methodInfo.Invoke(o, params);

Is this good enough, or are there better/faster/shorter ways?

As far as I’m concerned this is the best way and there isn’t really anything faster per say.

What about constructors, given that these methods are not static – can they simply be ignored?

You are still going to have to create an instance of t as shown in my example. This will use the default constructor with no arguments. If you need to pass arguments you can, just see the MSDN documentation and modify it as such.