How To Fix WD291 - Container element & is not multiline -> Appending not allowed

SAP Error Message - Details

• Message type: E = Error

• Message class: WD - Workflow definition

• Message number: 291

• Message text: Container element & is not multiline -> Appending not allowed

What causes this issue?

You are trying to append values to container element &V1&. This is not
possible, because the container element is not defined as a multi-line
element.

System Response

Appending values is only possible for multi-line elements. For other
container elements, only the assignment operator can be used.

How to fix this error?

Enter a multi-line element as the result element for the assignment or
use the assignment operator "=".

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message WD291 - Container element & is not multiline -> Appending not allowed ?

  Certainly! Here's a detailed explanation of the SAP error message:
  
  SAP Error Message:
  WD291 Container element & is not multiline -> Appending not allowed
  
  Meaning / Cause:
  This error occurs in Web Dynpro ABAP when you try to append data to a container element that is not defined as multiline. In Web Dynpro, container elements can be either single-line or multiline. Appending data (e.g., appending rows to an internal table or adding multiple entries) is only allowed if the container element is multiline.
  If you attempt to append data to a container element that is defined as a single-line element (e.g., a single string or a single structure), the framework raises this error.
  
  When does it happen?
  
  When you use the method APPEND or try to add multiple entries to a container element that is not designed to hold multiple entries.
  When the context node or attribute is defined as a single structure or scalar, but your code tries to treat it as a table or multiline element.
  When the UI element bound to the context element expects a multiline structure (like a table UI element), but the context element is not multiline.
  
  
  How to identify the problem:
  
  Check the context node or attribute definition in the Web Dynpro component.
  Verify if the context element you are trying to append to is defined as a single structure or a table.
  Check the UI element binding: if the UI element is a table or list, the context element must be multiline (table).
  Review the code where you do the append operation.
  
  
  Solution:
  
  
  Make the container element multiline:
  
  In the Web Dynpro context, change the context node or attribute to be a table (multiline) instead of a single structure.
  For example, if you have a context node MY_NODE defined as a single structure, change it to a table node by setting the cardinality to 0..n or 1..n.
  
  
  
  Adjust your code to match the context element type:
  
  If the context element is single-line, do not use APPEND. Instead, use ASSIGN or SET to set the value.
  If you need to add multiple entries, ensure the context element is a table and then use APPEND.
  
  
  
  Check UI element binding:
  
  If the UI element is a table or list, ensure the context node is multiline.
  If the UI element is a single input field, the context element should be single-line.
  
  
  
  
  Example:
  Incorrect:
  DATA: lo_nd_my_node TYPE REF TO if_wd_context_node,
        lo_el_my_node TYPE REF TO if_wd_context_element.
  
  lo_nd_my_node = wd_context->get_child_node( name = 'MY_NODE' ).
  
  " MY_NODE is defined as a single structure, not a table
  lo_el_my_node = lo_nd_my_node->append_element( ). " This causes WD291 error
  Correct:
  
  Change MY_NODE to be a table node (cardinality 0..n).
  Then the append will work:
  
  lo_el_my_node = lo_nd_my_node->append_element( ).
  
  Related Information:
  
  Web Dynpro context nodes and attributes: single vs multiline
  UI element binding to context nodes
  Web Dynpro error messages documentation
  SAP Note or SAP Help Portal for Web Dynpro context handling
  
  
  Summary:
  
  
  
  Aspect
  Description
  
  
  
  
  Cause
  Trying to append to a context element that is not multiline (single structure or scalar).
  
  
  Solution
  Change the context element to be multiline (table) or avoid appending if single-line.
  
  
  Check
  Context node cardinality, UI element binding, and code logic for appending elements.
  
  
  Error Type
  Web Dynpro ABAP runtime error related to context handling.
  
  
  
  
  If you want, I can help you with the exact steps to change the context node or fix your code snippet. Just provide your context node definition or code snippet.