Calling a method with reflection that takes List as an argument

Question

4.33/5 (3 votes)

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I am struggling with calling a method with reflection...

The method signature is as follows: (changed the actual names...)

I have a interface called :

C#

public interface ICharacteristics
   {
       Score calculateScore(int ScorecardID, string UniqueID, ArrayList CharacteristicsValues);
   }

Then i have another class called:

C#

public class ScoreSmartCharValues
   {
       private string name;
       private int value;

       public int Value
       {
           get { return this.value; }
           set { this.value = value; }
       }

       public string Name
       {
           get { return name; }
           set { name = value; }
       }

       public ScoreSmartCharValues(int value, string name)
       {
           this.name = name;
           this.value = value;
       }

       public ScoreSmartCharValues()
       {

       }
   }

another class as follow:

SQL

public Score calculateScore(int ScorecardID, string UniquesID, ArrayList CharacteristicsValues)
        {

//Do something and return Score;

 return new Score();
}

Ok so once build... generates a DLL score.dll

The code that i use is simple to call reflection and invoke the method:

C#

Assembly assembly = Assembly.LoadFrom(@"Score.dll");


foreach (Type type in assembly.GetTypes())
            {
                // Pick up a class
                if (type.IsClass == true)
                {
                    Console.WriteLine("...Found Class : {0}", type.FullName);

                    // If it does not implement the IBase Interface, skip it
                    if (type.GetInterface("ICharacteristics") == null)
                    {
                        continue;
                    }

                    // If however, it does implement the IBase Interface,
                    // create an instance of the object
                    object ibaseObject = Activator.CreateInstance(type);
                    List<ScoreSmartCharValues> CharacteristicsValues = new List<ScoreSmartCharValues>();
                    CharacteristicsValues.Add(new ScoreSmartCharValues(1, "robs"));

                    object oObjectType = new object();
                    oObjectType = CharacteristicsValues;
                    // Create the parameter list
                    object[] arguments = new object[] { 10, "test", CharacteristicsValues };
                    object result;
                    // Dynamically Invoke the Object
                    Console.WriteLine("......Dynamically Invoking compute() on {0} Class", type.FullName);
               
                    result = type.InvokeMember("calculateScore",
                                                BindingFlags.Default |BindingFlags.InvokeMethod,
                                                null,
                                                ibaseObject,
                                                arguments);

                    Console.WriteLine("......Result is: {0}", result);
                }
            }

I get a method not found...

If i change the argument to send in Null in the place of the list it works...

Posted 2-Jun-11 21:33pm

BobbyBlueEyes

Updated 3-Jun-11 2:54am

v3

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Comments

BobJanova 3-Jun-11 8:55am

The reason the bind is failing is that the list type you generate (List<scoresmartcharvalues>) and the one the method accepts (List<Characteristics>) are not compatible. But please see Fredrik's answer and my comment thereunder: you don't need to use runtime binding at all.

3 solutions

Solution 1

Hi,

I would suggest to use dynamic where you find GetType() kind of code. Will give better performance too.

Soultion:

In this line

VB

// If however, it does implement the IBase Interface,
// create an instance of the object
object ibaseObject = Activator.CreateInstance(type);

instead of taking it as an object type above. Please use dynamic type as below and calling will simpler and better for sure.

MIDL

dynamic ibaseObject = Activator.CreateInstance(type);</pre>

Now,

Call whatever you want will be so easy and better in performance.

EX: ibaseObject.calculate(5, "name", arguments);

In above code, Like any other class object you can call those methods of class without any invoke method of reflection here.

Sure this will help you in reflection.

Hope this will help you

For more Information Please refer below link :

Perform Reflection and XML Traversing Using the dynamic Keyword in C#[^]

Thank You :)

Posted 2-Jun-11 21:57pm

Sanjay J Patolia

Updated 2-Jun-11 21:58pm

v2

Comments

BobbyBlueEyes 3-Jun-11 5:49am

Hi Thanks for the help,

But if i send in a List i still get the error, if i send in a null value then the method does get executed....

BobJanova 3-Jun-11 8:52am

dynamic still uses similar runtime binding methods under the covers to Reflection, so it doesn't really solve the problem, although it does make reflection-based code cleaner in the source.

Solution 2

Something like this?

C#

class Program {
    static void Main(string[] args) {

        List<ScoreSmartCharValues> characterstics = new List<ScoreSmartCharValues>();
        characterstics.Add(new ScoreSmartCharValues(1, "Hello"));
        characterstics.Add(new ScoreSmartCharValues(2, "World"));

        DoSomethingUsefull doSomethingUsefull = new DoSomethingUsefull();

        var methodToCall = doSomethingUsefull.GetType().GetMethod(
            "calculate",
            new Type[] {
            typeof(int),
            typeof(String),
            typeof(List<ScoreSmartCharValues>)
        }
        );
        methodToCall.Invoke(doSomethingUsefull, new Object[] { 1, "Foobar", characterstics });
        Console.WriteLine("Done");
        Console.ReadLine();
    }

}

public class DoSomethingUsefull {

    public int calculate(int number, string Name, List<ScoreSmartCharValues> Characterstics) {

        Console.WriteLine(number);
        Console.WriteLine(Name);
        foreach (var characterstic in Characterstics) {
            Console.WriteLine("{0} -> {1}", characterstic.Name, characterstic.Value);
        }

        return 0;

    }


}

public class ScoreSmartCharValues {
    private string name;
    private int value;

    public int Value {
        get { return this.value; }
        set { this.value = value; }
    }

    public string Name {
        get { return name; }
        set { name = value; }
    }

    public ScoreSmartCharValues(int value, string name) {
        this.name = name; this.value = value;
    }

    public ScoreSmartCharValues() { }
}

Posted 2-Jun-11 22:00pm

StM0n

Updated 3-Jun-11 2:08am

v2

Comments

BobbyBlueEyes 3-Jun-11 6:34am

The List being sent is of type class - that contains a int and a string as properties.

StM0n 3-Jun-11 6:58am

Sorry, I'm not quite sure what you mean. Did you mean the IList?

BobbyBlueEyes 3-Jun-11 7:55am

please see my code below:

public class ScoreSmartCharValues
{
private string name;
private int value;

public int Value
{
get { return this.value; }
set { this.value = value; }
}

public string Name
{
get { return name; }
set { name = value; }
}

public ScoreSmartCharValues(int value, string name)
{
this.name = name;
this.value = value;
}

public ScoreSmartCharValues()
{

}
}

I create a List of this type.

so this is my method signature:

Score calculateScore(int ScorecardID, string UniqueID, List<scoresmartcharvalues> CharacteristicsValues);

When i try to use reflection i cannot call the method...

I have change the signature to rather use a type of type object then it works fine...

StM0n 3-Jun-11 8:07am

Changed my solution...

StM0n 3-Jun-11 8:29am

Oops... now I see your Problem:

You do...


object oObjectType = new object();
oObjectType = CharacteristicsValues;

object[] arguments = new object[] { 10, "test", CharacteristicsValues };

but the signature of your method is...
public int void calculate(int number, string Name, List<characteristicsvalues> Characterstics)

Your invoke does not match the signature of the method you want to call...

BobbyBlueEyes 3-Jun-11 8:50am

ok let me change me code completely to show you what i'm doing ...

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Fredrik Bornander · Accepted Answer · 2011-06-02T22:01:00

I'm not sure, but it looks to me like you don't need the reflection bit at all.
Can't you just cast you ibaseObject to a ICharacteristics and invoke the calculateScore method normally?

If you do need to call it using reflection, here's a working example of what I think you're trying to do:

C#

using System;
using System.Collections;

namespace ReflectionTest
{

    public interface ICharacteristics
    {

        int calculate(int number, string Name, IList Characterstics);
    }

    public class MyImplementation : ICharacteristics
    {
        public int calculate(int number, string Name, IList Characterstics)
        {
            return 42;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            object[] instances = new object[] { "Test", new MyImplementation() };

            foreach (object instance in instances)
            {
                if (instance is ICharacteristics)
                {
                    Type type = instance.GetType();
                    object result = type.InvokeMember("calculate", System.Reflection.BindingFlags.InvokeMethod, null, instance,
                        new object[] { 1, "Name", new ArrayList()});
                }
            }
        }
    }
}

Hope this helps,
Fredrik Bornander

Calling a method with reflection that takes List as an argument

3 solutions

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