https://community.esri.com/t5/arcgis-rest-apis-and-services-questions/append-object-reference-not-set-to-an-instance-of/m-p/1205138#M4248 <P>I'm trying to append a file gdb to a feature layer on arcgis online (<A href="https://community.esri.com/t5/arcgis-rest-api-questions/copy-attachments-from-one-feature-layer-to-another/m-p/1202511" target="_self">because I want to merge them and keep the attachments and I think this is the only way</A>).</P><P>The gdb to append is a copy of a feature layer already on agol (exported as a fgdb). The destination feature layer is also a copy of a feature layer (exported as a fgdb and then republished).</P><P>I can append the gdb through the interface successfully, however I wish to do this automatically via the REST API.&nbsp;I keep getting a&nbsp;code 400 with the message "Object reference not set to an instance of an object.".</P><P>I have read here and there that this may be a problem with null values. I also thought the problem may be that some fields have a list of required values (domain), so I deleted those and&nbsp;I have trimmed down the fields and rows of both tables (source and destination) to troubleshoot and I have now basically 2 small tables (of 25 and 18 rows) with only the basic rows: FID, GlobalID, CreationDate, Creator, EditDate, Editor, t_id (another ID field that references another table) and attachments.<BR /><BR />I have tried specifying the upsert parameter to false, selecting only 1 field with fieldMappings and appendFields, but always getting the same error.</P><P><BR />What else can I check?</P><P>Thanks!</P> Mon, 22 Aug 2022 20:02:32 GMT mikaël 2022-08-22T20:02:32Z https://community.esri.com/t5/arcgis-rest-apis-and-services-questions/append-object-reference-not-set-to-an-instance-of/m-p/1205138#M4248 <P>I'm trying to append a file gdb to a feature layer on arcgis online (<A href="https://community.esri.com/t5/arcgis-rest-api-questions/copy-attachments-from-one-feature-layer-to-another/m-p/1202511" target="_self">because I want to merge them and keep the attachments and I think this is the only way</A>).</P><P>The gdb to append is a copy of a feature layer already on agol (exported as a fgdb). The destination feature layer is also a copy of a feature layer (exported as a fgdb and then republished).</P><P>I can append the gdb through the interface successfully, however I wish to do this automatically via the REST API.&nbsp;I keep getting a&nbsp;code 400 with the message "Object reference not set to an instance of an object.".</P><P>I have read here and there that this may be a problem with null values. I also thought the problem may be that some fields have a list of required values (domain), so I deleted those and&nbsp;I have trimmed down the fields and rows of both tables (source and destination) to troubleshoot and I have now basically 2 small tables (of 25 and 18 rows) with only the basic rows: FID, GlobalID, CreationDate, Creator, EditDate, Editor, t_id (another ID field that references another table) and attachments.<BR /><BR />I have tried specifying the upsert parameter to false, selecting only 1 field with fieldMappings and appendFields, but always getting the same error.</P><P><BR />What else can I check?</P><P>Thanks!</P> Mon, 22 Aug 2022 20:02:32 GMT https://community.esri.com/t5/arcgis-rest-apis-and-services-questions/append-object-reference-not-set-to-an-instance-of/m-p/1205138#M4248 mikaël 2022-08-22T20:02:32Z