Set lookup value from another item

Question

Hi!
I add to my list in SP 2013 new column like type Lookup field and select item from another document library
and display field select "Title". How i can set this filed value for new item from document library item?

Answer 1

Hi AllXander,
From your description, my understanding is that you want to set lookup field value with C# CSOM.
You could use method "FieldLookupValue()". Please refer to this code below to set lookup field value when add an new item to a list:
// replace your site URL
using (ClientContext context = new ClientContext("http://sp/sites/sp2013"))
// replace your user, password and domain
context.Credentials = new NetworkCredential("Administrator", "Access1", "contoso");
// the library that you get value for the lookup field
List list = context.Web.Lists.GetByTitle("Department");
context.Load(list);
context.ExecuteQuery();
CamlQuery query = new CamlQuery();
query.ViewXml = "<View/>";
ListItemCollection allContacts = list.GetItems(query);
context.Load(allContacts);
context.ExecuteQuery();
foreach (ListItem item in allContacts)
// replace the id that you want to set value to the lookup filed
if (item.Id == 1)
// replace the list title with your list that you want to add the item
List oList = context.Web.Lists.GetByTitle("Employee");
ListItemCreationInformation itemCreateInfo = new ListItemCreationInformation();
ListItem oListItem = oList.AddItem(itemCreateInfo);
oListItem["Title"] = "My New Item!";
// set the lookup field value
FieldLookupValue lookup = new FieldLookupValue();
lookup.LookupId = item.Id;
oListItem["Department"] = lookup;
oListItem.Update();
context.ExecuteQuery();
You could refer to this article about creating/updating/deleting a new item with C# CSOM:
http://www.c-sharpcorner.com/UploadFile/sagarp/create-update-delete-a-list-using-client-object-model-cso/
You could refer to this article about updating multi-value lookup column:
https://sunbin0704.wordpress.com/2013/10/11/update-multi-value-lookup-column-values-in-sharepoint-2010-using-managed-csom/
Best Regards,
Vincent Han
TechNet Community Support
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