Add user to SPO list programmatically

	using (ClientContext ctxObj = new ClientContext("http://sp2013/"))
	{
	Web objSite = ctxObj.Web;
	ctxObj.Load(objSite);
	ctxObj.ExecuteQuery();
	//User ClaimID would be ----i:0#.f|membership|domain\username
	/*
	i:0#w| =>
	i = identity
	# = user login name
	w = Windows
	i:0#.f =>
	f = membership provider name
	*/
	User objUser = objSite.EnsureUser("i:0#.f|membership|" + userId);
	ctxObj.Load(objUser);
	ctxObj.ExecuteQuery();
	FieldUserValue objUserValue = new FieldUserValue();
	objUserValue.LookupId = objUser.Id;
	List objListItems = objSite.Lists.GetByTitle("MyList");
	Microsoft.SharePoint.Client.ListItem objItem = objListItems.AddItem(new ListItemCreationInformation());
	objItem["UserName"] = objUserValue;
	objItem.Update();
	ctxObj.ExecuteQuery();
	}

view raw gistfile1.cs hosted with ❤ by GitHub