Programmatically retrieve all lookup field values

If you are using a lookup field in code and need to retrieve the values available through that lookup, you can do so by writing a generic method to return all possible values in a collection for you to use as needed. Here is an example:

public static List<SPFieldLookupValue> GetLookupFieldValues(SPList list, string fieldName)
    {
        var results = new List<SPFieldLookupValue>();
        var field = list.Fields.GetField(fieldName);
 
        if (field.Type != SPFieldType.Lookup) throw new SPException(String.Format("The field {0} is not a lookup field.", fieldName));
 
        var lookupField = field as SPFieldLookup;
        var lookupList = list.ParentWeb.Lists[Guid.Parse(lookupField.LookupList)];
        var query = new SPQuery();
 
        query.Query = String.Format("<OrderBy><FieldRef Name='{0}'/></OrderBy>", lookupField.LookupField);
 
        foreach (SPListItem item in lookupList.GetItems(query))
        {
            results.Add(new SPFieldLookupValue(item.ID, item[lookupField.LookupField].ToString()));
        }
 
        return results;
    }

Then to use it, your code would look something like this:

var list = SPContext.Current.Web.Lists["My List"];
var results = GetLookupFieldValues(list, "Actual City");
 
foreach (SPFieldLookupValue result in results)
{
    var value = result.LookupValue;
    var id = result.LookupId;
}