Change the value of a custom field in Bitrix24 when creating a new task?

Question

Bitrix24

I'm trying to change the value of a custom field through the onBeforeTaskAdd event, standard fields are easy to change, but not custom fields. I got the arFields array before saving it and the value I need is present in the array. After saving, this value is reset to the preset value.
I need: in the "list of sections of the infoblock" field, select the id of the infoblock through the script in init.php, which I successfully do and write it (id) into the value of the task field.
It's simple, but it doesn't work...

Answer 1

1) In the "Binding to infoblock sections" type field, you cannot specify the ID of the infoblock.
The infoblock ID is selected when creating a field for the task entity, and when creating the task itself, only section IDs are specified.
2) The OnBeforeTaskAdd event takes as an output parameter $arFields, an associative array of fields for the task being created.
By specifying an event handler, are you explicitly passing that you are receiving it by reference? there is a very big difference
between and 3) Handlers are built in such a way that they are called sequentially. There is a possibility that another handler following yours overwrites your value
function handleBeforeTaskAdd( $arFields )
function handleBeforeTaskAdd( &$arFields )