I am developping a project using Twincat3 and C# ADS for the HMI.

For structure purpose, i want to use Twincat POO. I am new to Twincat and dont understand how to connect nested child objects to my HMI using ADS handler.

I have 1 parent function block

//Example
FUNCTION_BLOCK FB_Parent
VAR
    iParentVariable: INT;
END_VAR

and multiple child function block that extends FB_Parent

//Example
FUNCTION_BLOCK FB_Child
VAR
    iChildVariable: INT;
END_VAR

In my program, i have an array of FB_Parent. On initialization command from my custom HMI (C#), i create new FB_Child dynamically:

// Example
fbChild := __NEW(FB_Child);
array[0] := fbChild^;
__DELETE(fbChild);

The problem is that I can’t create handler and access child variable from my HMI (C#):

client = new AdsClient
{
    Timeout = 500
};
client.Connect(parameters.AmsNetID, parameters.AdsPort);
handler = client.CreateVariableHandle("PRG_MAIN.arrConveyors[0].iChildVariable");

How can i still use POO and dynamic object creation in Twincat and access child variable in C# trough ADS ?

Thanks for you help !

I tried to change the definition of my array:

1. Using POINTER OF FB_Parent
2. Using Interface instead of Parent class

Nothing worked.