Labels do not appear for Map Image Layer data when concatenating a NULL field value in labelExpression for ArcGIS Maps SDK for JavaScript.

Solución alternativa

Opt for either of the following workarounds:

• Use the Feature Layer class in the ArcGIS Maps SDK for JavaScript and specify the Map Image Layer's sublayer ID in the URL.
• Publish the layer as a feature service instead of a map image service, and use the Feature Layer class in ArcGIS Maps SDK for JavaScript.

Pasos para reproducir