Activator.CreateInstance() throw System.MissingMethodException while create the instance C#

Question

I need to call the different classes based on the requirement. For that, I have used Activator.CreateInstance() to achieve my goal. But, I can successfully access the specific class without passing the argument. But, while pass the argument I'm facing the problem. Here, I have posted my sample code.

class Program
{
    private static readonly object[] activationAttributes;

    static void Main(string[] args)
    {
        Console.WriteLine("Hello World!");

        ObjectHandle obj = Activator.CreateInstance("JsonGenerator", "JsonGenerator.MyClass2", true, System.Reflection.BindingFlags.Default, null, new object[] { "TestValue" }, null, activationAttributes); // Not working
        //ObjectHandle obj = Activator.CreateInstance("JsonGenerator", "JsonGenerator.MyClass2"); // This kind of call work.
        ParentClass parent = (ParentClass)obj.Unwrap();

        parent.PerformFunction();
    }
}

public abstract class ParentClass
{
    public abstract void PerformFunction();
}
class MyClass1 : ParentClass
{
    public MyClass1(object[] args)
    {

    }

    public override void PerformFunction()
    {
        Console.WriteLine("Override insidet the class1");
    }
}

class MyClass2 : ParentClass
{
    public MyClass2(object[] args)
    {

    }

    public override void PerformFunction()
    {
        Console.WriteLine("Override insidet the class2");
    }
}

The below error message thrown while run the program

Unhandled exception. System.MissingMethodException: Constructor on type 'JsonGenerator.MyClass2' not found.
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Activator.CreateInstanceInternal(String assemblyString, String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(String assemblyName, String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)

It would be much appreciated if anyone can help on this.

Thanks,

Does this answer your question? [How to Pass Parameters to Activator.CreateInstance()](https://stackoverflow.com/questions/2451336/how-to-pass-parameters-to-activator-createinstancet) — Pavel Anikhouski, Jun 12 '20 at 10:21
Hi Pavel, Actually for this example I have the both classes in same place. But in real implementation those classes will be different assemblies. — Ramachandran, Jun 12 '20 at 10:53

score 0 · Answer 1 · answered Jun 12 '20 at 13:16

0

To pass the string as argument, fixed my issue. Infact, the CreateInstance unpacked the object and invoked the corresponding constructor.

public MyClass1(string args)
{

}

And,

public MyClass2(string args)
{

}

Thanks,

answered Jun 12 '20 at 13:16

Ramachandran

103
12

Activator.CreateInstance() throw System.MissingMethodException while create the instance C#

1 Answers1