Question

I have a method as shown below…

public bool MakeRequest(string[] args)
    {
        try
        {
            sXmlRequest = args[0];
            sResponse = "";
            Console.WriteLine(sXmlRequest);
            sw.Write(sXmlRequest);
            sw.Flush();
            sResponse = sr.ReadToEnd();
            return true;
        }
        catch (Exception e)
        {
            sResponse = e.Message;
            return false;
        }

    }

I have to call this method using Reflection, because of the way the entire framework is setup.

Here is the code I’m using to call it

string[] innerargs = {"Dummy Args"};
string pAssembly = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location) + "\\TCPConnector.dll";
Assembly assemblyInstance = Assembly.LoadFrom(pAssembly);
Type tConnector = assemblyInstance.GetType("Fit.TcpConnector");
Object oLateBound = assemblyInstance.CreateInstance(tConnector.FullName);

result = tConnector.InvokeMember("MakeRequest", BindingFlags.Public | BindingFlags.InvokeMethod | BindingFlags.Instance, null, oLateBound, innerargs);

This is returning me MissingMethodException saying the method Fit.TcpConnector.MakeRequest is not found.

However, if I change the signature of the MakeRequest to

  public bool MakeRequest(string args)

instead of

  public bool MakeRequest(string[] args)

then, it is working. Can anybody point me in right direction in calling the function which takes array as its parameter?

Answer 1

You have to pass it an array that contains your array:

tConnector.InvokeMember(
    "MakeRequest",
    BindingFlags.Public | BindingFlags.InvokeMethod | BindingFlags.Instance,
    null, oLateBound, new object[] { innerargs });

That’s because each item in the array you pass to the method represents one parameter to the function. And since you function has one parameter of type string[], you need to give it an array that contains one item of type string[].

That being said, I think using GetMethod() and Invoke() is clearer than InvokeMember():

var makeRequestMethod = tConnector.GetMethod("MakeRequest");
makeRequestMethod.Invoke(oLateBound, new object[] { innerargs });

Your incorrect code compiles because of array covariance as Eric Lippert pointed out in his answer.