Updating a multiselect field via REST API 2010

Question

Can you update a mulivalue choice field via REST API in SharePoint 2010?

If I perform a simple GET I receive:

{
    "d": {
        "__metadata": {
            "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeed(1)",
            "etag": "W/\"9\"",
            "type": "Microsoft.SharePoint.DataService.MarketNeedItem"
        },
        "ContentTypeID": "0x0100D93C50E37E1AA144B940BA546F3287FF",
        "Title": "I changed the title.",
        "ProblemStatement": "Shellworker Streetwise A Fret Whishted Shalt Fiver Wool Tv. Hoc Positum In Phaedro A Platone Probavit Epicurus. Theraphosoid Tee Ha, Flip, If Teal If Atwirl A.",
        "RequestorOrganization": {
            "__deferred": {
                "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeed(1)/RequestorOrganization"
            }
        },
        "RequestorOrganizationValue": null,
        "Confidentiality": "None",
        "MarketNeedID": "7542f43a-093b-4bd4-a29d-101eea7e166b",
        "Request_ID": "NONE-00001",
        "CustomerRequestor": {
            "__deferred": {
                "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeed(1)/CustomerRequestor"
            }
        },
        "CustomerRequestorId": null,
        "ContactInformation": null,
        "Grouping": {
            "results": [
                {
                    "__metadata": {
                        "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('System%20Software')",
                        "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
                    },
                    "Value": "System Software"
                },
                {
                    "__metadata": {
                        "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('Factory%20Fit%20System%20Software')",
                        "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
                    },
                    "Value": "Factory Fit System Software"
                }
            ]
        }
    }
}

I am sending the following payload as a POST with merge and check the etag:

{
"Title":"I changed the title again.",
    "Grouping": {
        "results": [
            {
                "__metadata": {
                    "uri": "http://dev.domain.net/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('System%20Software')",
                    "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
                },
                "Value": "System Software"
            },
            {
                "__metadata": {
                    "uri": "http://dev.domain.net/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('Factory%20Fit%20System%20Software')",
                    "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
                },
                "Value": "Factory Fit System Software"
            },
            {
                "__metadata": {
                    "uri": "http://dev.domain.net/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('Special%20Kitting')",
                    "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
                },
                "Value": "Special Kitting"
            }
        ]
    }
}

And I get the following error:

{
    "error": {
        "code": "",
        "message": {
            "lang": "en-US",
            "value": "Error processing request stream. The payload must represent a valid array format for collections."
        }
    }
}

If I remove the "Grouping" object and just change the title, everything works like a charm. But that is of little use to me.

Answer 1

To add an item to the array you send a POST to the URL of the item you wish to update: dev.domain.com/sites/plm/_vti_bin/ListData.svc/MarketNeed(1)

with the following payload:

{
    "Grouping": [
        {
            "__metadata": {
                "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('Special%20Kitting')",
                "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
            }
        }
    ]
}

To delete the same selection from the list items choice field you send a DELETE to

dev.domain.com/sites/plm/_vti_bin/ListData.svc/MarketNeed(1)/$links/Grouping('Special%20Kitting')

If you send a payload with the value attribute you will get an error that deep updates are not allowed.

{
    "Grouping": [
        {
            "__metadata": {
                "uri": "http://ctct-dev.ctct.net/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('Research')",
                "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
            },
            "Value":"Research"
        }
    ]
}

To remove all selections from the item's field you would need to post to the URL that is unique to each selection. For example if my list item was returning a "Grouping" field with the following contents:

{
    "Grouping": {
        "results": [
            {
                "__metadata": {
                    "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('System%20Software')",
                    "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
                },
                "Value": "CAES System Software"
            },
            {
                "__metadata": {
                    "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('Factory%20Fit%20System%20Software')",
                    "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
                },
                "Value": "Factory Fit System Software"
            },
            {
                "__metadata": {
                    "uri": "http://dev.domain/sites/plm/_vti_bin/ListData.svc/MarketNeedGrouping('Research')",
                    "type": "Microsoft.SharePoint.DataService.MarketNeedGroupingValue"
                },
                "Value": "Research"
            }
        ]
    }
}

I would need to send separate deletes to 3 URLs .../_vti_bin/ListData.svc/MarketNeed(1)/$links/Grouping('Factory%20Fit%20System%20Software') .../_vti_bin/ListData.svc/MarketNeed(1)/$links/Grouping('Special%20Kitting') .../_vti_bin/ListData.svc/MarketNeed(1)/$links/Grouping('Research')