Ad:

C# Discussion Thread
Unsolved
Views: 46298

Nov 23rd, 2007

Reflection Invoke Method w/ Params

Expand Post »

Hi All,

A long time ago I researched Reflection and created a solution demoing my learnt capabilities from it.

In my example I did not pass any arguments into the Invocation of the method call using reflection.

I went to tackle this and I seem to be hitting a few dead ends.

Here is the method I call from my Main method in another class.

C# Syntax (Toggle Plain Text)
public void RunClass(string dllName, string className, string methodName, params Object[] parameters)
        {
            // Create the assemblies from our current DLL.
            Assembly _Assemblies = Assembly.LoadFrom(dllName);
 
            // Get the type that we want from the assemblies.
            //  IE: This would be the fully qualified class name (including namespace)
            //  Example: "Reflectionism.Examples.Example1" or "Reflectionism.Examples.Example2"
            Type _Type = null;
            try
            {
                 _Type = _Assemblies.GetType(className);
            }
            catch (Exception ex)
            {
                Console.WriteLine("\n\nError - couldn't obtain classrd from " + className);
                Console.WriteLine("EXCEPTION OUTPUT\n" + ex.Message + "\n" + ex.InnerException);
                return;
            }
 
            // Get the desired method we want from the target type.
            MethodInfo _MethodInfo = null;
            try
            {
                _MethodInfo = _Type.GetMethod(methodName, new Type[] { typeof(Object[]) });
            }
            catch (Exception ex)
            {
                Console.WriteLine("\n\nError - couldn't obtain method " + methodName + " from " + className);
                Console.WriteLine("EXCEPTION OUTPUT\n" + ex.Message + "\n" + ex.InnerException);
                return;
            }
 
            // The first parameter to pass into the Invoke Method coming up.
            Object _InvokeParam1 = Activator.CreateInstance(_Type);
            //Object[] _Params = new Object[] { parameters };
 
            // This calls the target method ("DisplayMyself").
            //  NOTE: I'm not passing any arguments down to the method being invoked.
            //  Therefore, I'm passing null as my argument, otherwise Invoke takes an
            //  array of Objects.
            _MethodInfo.Invoke(_InvokeParam1, new Object[] { _parameters});
        }
public void RunClass(string dllName, string className, string methodName, params Object[] parameters)
        {
            // Create the assemblies from our current DLL.
            Assembly _Assemblies = Assembly.LoadFrom(dllName);

            // Get the type that we want from the assemblies.
            //  IE: This would be the fully qualified class name (including namespace)
            //  Example: "Reflectionism.Examples.Example1" or "Reflectionism.Examples.Example2"
            Type _Type = null;
            try
            {
                 _Type = _Assemblies.GetType(className);
            }
            catch (Exception ex)
            {
                Console.WriteLine("\n\nError - couldn't obtain classrd from " + className);
                Console.WriteLine("EXCEPTION OUTPUT\n" + ex.Message + "\n" + ex.InnerException);
                return;
            }

            // Get the desired method we want from the target type.
            MethodInfo _MethodInfo = null;
            try
            {
                _MethodInfo = _Type.GetMethod(methodName, new Type[] { typeof(Object[]) });
            }
            catch (Exception ex)
            {
                Console.WriteLine("\n\nError - couldn't obtain method " + methodName + " from " + className);
                Console.WriteLine("EXCEPTION OUTPUT\n" + ex.Message + "\n" + ex.InnerException);
                return;
            }
        
            // The first parameter to pass into the Invoke Method coming up.
            Object _InvokeParam1 = Activator.CreateInstance(_Type);
            //Object[] _Params = new Object[] { parameters };

            // This calls the target method ("DisplayMyself").
            //  NOTE: I'm not passing any arguments down to the method being invoked.
            //  Therefore, I'm passing null as my argument, otherwise Invoke takes an
            //  array of Objects.
            _MethodInfo.Invoke(_InvokeParam1, new Object[] { _parameters});
        }

I call this RunClass method from my Main method like this:

C# Syntax (Toggle Plain Text)
//_UserInputParam is a Console.ReadLine() object (In my testing I am passing '5' to this call).
_Main._ReflectMain.RunClass(_UserInputDLL, _UserInputClass, _UserInputMethod, Int32.Parse(_UserInputParam));
//_UserInputParam is a Console.ReadLine() object (In my testing I am passing '5' to this call).
_Main._ReflectMain.RunClass(_UserInputDLL, _UserInputClass, _UserInputMethod, Int32.Parse(_UserInputParam));

The class that is being called by the invocation of the reflection method call is set up like this:

C# Syntax (Toggle Plain Text)
public void DisplayMyself(params Object[] parameters)
        {
            if (parameters.Length <= 0)
            {
                Console.WriteLine("Hello! I am " + this.ToString());
                return;
            }
            Console.WriteLine("Parameter Found in: " + this.ToString() + "__ Param was: ");
            for (int i = 0; i < parameters.Length; i++)
            {
                Console.WriteLine(parameters[i]);
            }
        }
public void DisplayMyself(params Object[] parameters)
        {
            if (parameters.Length <= 0)
            {
                Console.WriteLine("Hello! I am " + this.ToString());
                return;
            }
            Console.WriteLine("Parameter Found in: " + this.ToString() + "__ Param was: ");
            for (int i = 0; i < parameters.Length; i++)
            {
                Console.WriteLine(parameters[i]);
            }
        }

The error I'm receiving is:

C# Syntax (Toggle Plain Text)
Object reference not set to instance of an object. It occurs on the line
Object reference not set to instance of an object. It occurs on the line

And it occurs on the line:

C# Syntax (Toggle Plain Text)
_MethodInfo.Invoke(_InvokeParam1, new Object[] { parameters });
_MethodInfo.Invoke(_InvokeParam1, new Object[] { parameters });

Even though when debugging parameters, it has the object '5' within it (or whatever the user inputs into the console.readline (and outputted through int32.parse() call).

Any help/insight would be appreciated.

Thanks,
-Catch

Similar Threads

Threading, Delegates and the Invoke method. in VB.NET
Retreiving/Allocating a new type during runtime with Reflection in C#
Generic method parser / invoker in C#
Invoking in Java
I need help..urgently in VB.NET

mariocatch

Reputation Points: 11

Solved Threads: 17

Junior Poster

Offline

103 posts
since Apr 2007

Permalink

Mar 9th, 2008

Re: Reflection Invoke Method w/ Params

Hey man, I am having the same issue, if youknow of a solution let me know, otherwise i'll keep searching and let you know if I do

bodikon

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

12 posts
since Jun 2006

Permalink

Mar 9th, 2008

Re: Reflection Invoke Method w/ Params

Please, send me your project on RamyMahrous@gmail.com I'll debug it and tell you the problem en shaa ALLAH

Ramy Mahrous

Featured Poster

Reputation Points: 480

Solved Threads: 276

Postaholic

Offline

2,189 posts
since Aug 2006

Permalink

Jun 20th, 2008

Re: Reflection Invoke Method w/ Params

I've been working with c# since only a year, but I figured this for a c# windows service I've made that calls a vb6 class object with no less then 52 arguments....

hope it will help someone.

C# Syntax (Toggle Plain Text)
using System;
using System.Reflection;
 
private Type ProgType =  Type.GetTypeFromProgID("myvb6dll.dvrObj");   // Assign Type to the Class Type
object o = Activator.CreateInstance(ProgType);
object returnValue;
 
// Create object that will holds arguments to pass to InvokeMember
// See VB6 Newobject project for list of arguments 
object[] arguments = new object[52];
arguments[0] = objectClass;
.......
.......
arguments[51] = objectVerifyThis;
 
returnValue = ProgType.InvokeMember("makeCall", BindingFlags.InvokeMethod, null, o, arguments);
resFonction = returnValue.ToString();
using System;
using System.Reflection;

private Type ProgType =  Type.GetTypeFromProgID("myvb6dll.dvrObj");   // Assign Type to the Class Type
object o = Activator.CreateInstance(ProgType);
object returnValue;

// Create object that will holds arguments to pass to InvokeMember
// See VB6 Newobject project for list of arguments 
object[] arguments = new object[52];
arguments[0] = objectClass;
.......
.......
arguments[51] = objectVerifyThis;

returnValue = ProgType.InvokeMember("makeCall", BindingFlags.InvokeMethod, null, o, arguments);
resFonction = returnValue.ToString();

Let me know if it's clear enough...
Thanks.

floydus

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

8 posts
since Dec 2006

This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

Previous Thread in C# Forum Timeline: Refer to an instance using a variable

Next Thread in C# Forum Timeline: How to Blink an image

DaniWeb Message

Cancel Changes

User Name
Password