Update MultiValue Lookup Column using CSOM

Question

I am trying to update a multi value lookup column in SP 2013 On Premise. I have gone through various forums for achieving this and as suggested, I am getting values in SPFieldLookupValueCollection. Sample values in this are of the format:

4;#N/A

The problem I am facing is if I try to update the column using :

item["ColumnName"] = SPfieldLookupvaluecollection object

I am getting an exception saying that item is being updated in the wrong format. the closest I've come to updating the lookup column is by using a foreach loop and iterating the lookupvaluecollection. But this doesn't help me since I have multiple values in the SPfieldLookupvaluecollection object and only the last value is getting updated. Any help would be appreciated.

Thanks

Edit : Updating with the code snippet.

Microsoft.SharePoint.Client.File newfile = myclientcontext.Web.GetFileByServerRelativeUrl("Relative path to file here"); myclientcontext.load(newfile); ListItem item = newfile.ListItemAllFields;

//I'm reading lookup values from a csv file and updating accordingly

if (rowfilter.ItemArray[0].ToString() != "") { string[] values = rowfilter.ItemArray[0].ToString().Split(';');

SPFieldLookupValueCollection fieldlookup = GetLookupFieldIDs(values, "LookupListName"); }

//Above method returns values in the format 4;#N/A 106;#Building //This is what i've tried

1. item["ColumnName"] = fieldlookup;
2. var arraylist = new ArrayList(); foreach (SPFieldLookupValue value in fieldlookup) { arraylist.Add(value.LookupId); } item["ColumnName"] = arraylist.ToArray();

However I get an error always. Any help would be appreciated.

Answer 1

We can use the following CSOM code snippet to update multiple lookup columns.

var siteUrl = "http://sp2013";
var username = "username";
var password = "password";
var domain = "domain";
var listName = "customlist";
var itemId = 1;
var lookupColumnName = "MultipleLookup";
using (ClientContext ctx = new ClientContext(siteUrl))
{
    ctx.Credentials = new NetworkCredential(username, password, domain);
    var list = ctx.Web.Lists.GetByTitle(listName);
    var item = list.GetItemById(itemId);               
    ctx.Load(item, i => i[lookupColumnName]);
    ctx.ExecuteQuery();
    var lookupValues = new ArrayList();            
    var lookupValue = new FieldLookupValue { LookupId = 5 };
    lookupValues.Add(lookupValue);
    var lookupValue1 = new FieldLookupValue { LookupId = 2 };
    lookupValues.Add(lookupValue1);
    item[lookupColumnName] = lookupValues.ToArray();
    item.Update();
    ctx.ExecuteQuery();
}