C#

public LookupEntity AddLookup(LookupEntity entity)
{
    using (FMGDataContext dc = getDataContext())
    {
        // See if a lookup with the same Caption already exists
        var lookupExists = dc.Lookups.Where(l => l.Caption.Trim().ToLower() == entity.Caption.Trim().ToLower() &&
                                            l.LookupCode.Trim().ToLower() == entity.LookupCode.Trim().ToLower()).Any();

        // If the lookup doesn't already exist...
        if (!lookupExists)
        {
            // Add the lookup
            Lookup newLookup = new Lookup
            {
                LookupCode = entity.LookupCode,
                LookupTypeName = entity.LookupTypeName,
                Caption = entity.Caption,
                Description = entity.Description,
                ParentId = entity.ParentId ?? 0,
            };

            dc.Lookups.InsertOnSubmit(newLookup);
                    
            try
            {
                dc.SubmitChanges();

                entity.Id = newLookup.LookupId;
            }
            catch (Exception e)
            {
                // Handle exception here
            }
        }
        else
        {
            throw new DuplicateLookupException(string.Format("Lookup {0} already exists", entity.Caption));
        }
    }

    return entity;
}

public class _ResponseBase
{
    [DataMember]
    public Result Result { get; set; }

    [DataMember]
    public string Message { get; set; }

    private Exception _Exception;
    [DataMember]
    public Exception Exception
    {
        get { return _Exception; }
        set
        {
            if (_Exception != value)
            {
                _Exception = value;

                Message = _Exception.Message;
                Result = Result.Failure;
            }
        }
    }
}

public AddLookupResponse AddLookup(LookupEntity entity)
{
    AddLookupResponse response = new AddLookupResponse();

    using (FalconDataContext dc = getDataContext())
    {
        bool exsits = (from l in dc.Lookups
                        where l.LookupCode.Trim().ToLower() == entity.LookupCode.Trim().ToLower()
                        select l).Any();

        if (exsits)
        {
            response.Result = Result.Failure;
            response.Message = string.Format("Lookup code '{0}' already exists in the Lookups table", entity.LookupCode);
        }
        else
        {
            Lookup newRecord = new Lookup
            {
                LookupCode = entity.LookupCode,
                LookupName = entity.LookupName,
                Caption = entity.Caption,
                Description = entity.Description,
                SystemCode = entity.SystemCode,
                ParentId = entity.ParentId
            };

            dc.Lookups.InsertOnSubmit(newRecord);

            try
            {
                dc.SubmitChanges();

                entity.Id = newRecord.LookupId;
                response.Data = entity;
            }
            catch (Exception e)
            {
                response.Exception = e;
            }
        }
    }

    return response;
}

AddLookupResponse response = Engine.APIProxy.AddLookup(SelectedLookupItem);

if (response.Result == Result.Success)
{
    // Do something
}
else
{
	HandleResponse(response);
}