How to set multiple values in sharepoint lookup field using c# [duplicate]

Question

I want to set the multiple values in lookup column. my string format is id#;id#;id#; but it is giving error.

Answer 1

Try this below code:

String [] idsCol = id.split("#;");       //id = your string "id#;id#;id#;"
SPFieldLookupValueCollection fieldValues = new SPFieldLookupValueCollection();
foreach(string s in idsCol)
{
    fieldValues.Add(new SPFieldLookupValue{LookupId=(Convert.ToInt32(s))});
}
SPListItem newItem = list.Items.Add();   //list = your desired list object
newItem["Your column name"] = fieldValues;
newItem.Update();

Answer 2

 List<FieldLookupValue> branchLookupValueList = new List<FieldLookupValue>();
                string[] branchIds = userInformation.Branch_Name.Split(delimiters, StringSplitOptions.RemoveEmptyEntries);
                foreach (var branchId in branchIds)
                {
                    FieldLookupValue LookupColBranch = new FieldLookupValue();
                    LookupColBranch.LookupId = Convert.ToInt32(branchId);
                    branchLookupValueList.Add(LookupColBranch);
                }
                NewItem["BranchName"] = branchLookupValueList;