Question

I have am creating an Instance dynamically using Activator.CreateInstance. However, it is saying object cannot be null on every attempt. Pasting the code below. Am I doing anything wrong?

Is there any problem if

Activator.CreateInstance

replaces the conventional switch/case statements for determining the object type in the run-time? Thanks.

public abstract  class Base
{
    public abstract void Func();

}
public  class  Derived:Base
{
    public override void Func()
    {
        MessageBox.Show("Derived First");
    }
}

public class Derived2 : Base
{
    public override void Func()
    {
        MessageBox.Show("Derived Second");
    }
}

private void button1_Click(object sender, EventArgs e)
{
    // I was trying to make use of the overladed version 
    // where it takes the Type as parameter.
    BaseClass report = 
       (BaseClass) Activator.CreateInstance(Type.GetType("Derived")); 
    report.Func();
}

Answer 1

From the documentation of the typeName parameter of Type.GetType:

The assembly-qualified name of the type to get. See
AssemblyQualifiedName. If the type is in the currently executing
assembly or in Mscorlib.dll, it is sufficient to supply the type name
qualified by its namespace.

This means that you need to (at least) pass the namespace as well:

BaseClass report = (BaseClass) Activator.CreateInstance(Type.GetType("YourNamespace.Derived"));