C# – Using C# reflection to call a constructor

cconstructorreflection

I have the following scenario:

class Addition{
 public Addition(int a){ a=5; }
 public static int add(int a,int b) {return a+b; }
}

I am calling add in another class by:

string s="add";
typeof(Addition).GetMethod(s).Invoke(null, new object[] {10,12}) //this returns 22

I need a way similar to the above reflection statement to create a new object of type Addition using Addition(int a)

So I have string s= "Addition", I want to create a new object using reflection.

Is this possible?

Best Answer

I don't think GetMethod will do it, no - but GetConstructor will.

using System;
using System.Reflection;

class Addition
{
    public Addition(int a)
    {
        Console.WriteLine("Constructor called, a={0}", a);
    }
}

class Test
{
    static void Main()
    {
        Type type = typeof(Addition);
        ConstructorInfo ctor = type.GetConstructor(new[] { typeof(int) });
        object instance = ctor.Invoke(new object[] { 10 });
    }
}

EDIT: Yes, Activator.CreateInstance will work too. Use GetConstructor if you want to have more control over things, find out the parameter names etc. Activator.CreateInstance is great if you just want to call the constructor though.

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