Hi Nik,

Thanks for pointing me in the right direction that was exactly what I was looking for.

https://our.umbraco.com/documentation/reference/management/services/membertypeservice/

For completion here is the code I wrote.

I am using the SavingEvent when users are adding new member marketing filters. I then use the MemberTypeService to check these fields exist and they are the correct datatype.

If the field alias doesn't exist or the datatype is incorrect for the type of filter they are adding then an error is thrown and the filter isn't saved.

private void ContentService_Saving(IContentService sender, ContentSavingEventArgs args)
        {
            foreach (var node in args.SavedEntities)
            {
                try
                {
                    string propertyType = "";
                    string fieldAlias = "";

                    if (node.ContentType.Alias == "umb8smmBooleanFilter")
                    {
                        propertyType = "Umbraco.TrueFalse";
                        fieldAlias = (string)node.Properties["memberFieldAlias"].GetValue();
                    }
                    else if (node.ContentType.Alias == "umb8smmDateFilter")
                    {
                        propertyType = "Umbraco.DateTime";
                        fieldAlias = (string)node.Properties["memberFieldAlias"].GetValue();
                    }
                    else if (node.ContentType.Alias == "umb8smmDecimalFilter")
                    {
                        propertyType = "Umbraco.Decimal";
                        fieldAlias = (string)node.Properties["memberFieldAlias"].GetValue();
                    }
                    else if (node.ContentType.Alias == "umb8smmNumericFilter")
                    {
                        propertyType = "Umbraco.Integer";
                        fieldAlias = (string)node.Properties["memberFieldAlias"].GetValue();
                    }
                    else if (node.ContentType.Alias == "umb8smmTextFilter")
                    {
                        propertyType = "Umbraco.TextBox";
                        fieldAlias = (string)node.Properties["memberFieldAlias"].GetValue();
                    }

                    if(!string.IsNullOrEmpty(propertyType) && !string.IsNullOrEmpty(fieldAlias))
                    {
                        var memberType = _memberTypeService.GetAll().FirstOrDefault();
                        if (memberType != null)
                        {
                            var boolField = memberType.PropertyTypes.FirstOrDefault(x => x.Alias == fieldAlias && x.PropertyEditorAlias == propertyType);
                            if (boolField == null)
                            {
                                args.Cancel = true;
                                args.Messages.Add(new EventMessage("Error Adding Filter!", "No " + propertyType + " field matching the provided alias (" + fieldAlias + ") was found on the member type (" + memberType.Alias + ").", EventMessageType.Error));
                            }
                        }
                        else
                        {
                            args.Cancel = true;
                            args.Messages.Add(new EventMessage("Error Adding Filter!", "There was no member type found. Please check your default Umrbaco member section setup.", EventMessageType.Error));
                        }
                    }
                }
                catch (Exception e)
                {
                    _logger.Error<SavingEvent>("ContentService_Saving | Exception: {0} | Message: {1}", e.InnerException != null ? e.InnerException.ToString() : "", e.Message != null ? e.Message.ToString() : "");
                }
            }
        }

Thanks for your assistance Nik & Ravi

Regards

David