PropertyGrib and ComboBox

        public string Error { get; private set; }

        public string this[string columnName]
        {
            get
            {
                return GetErrorCore(columnName);
            }
        }

        private string GetErrorCore(string columnName)
        {
            Error = GetError(columnName);
            return Error;
        }

        protected virtual string GetError(string columnName)
        {
            return null;
        }

 If I set a TracePoint on the get of the this[string columnName] property, I see that this accessor is called 5 times when I modified a property of a combobox (ie:FontStyle) and one time if I modify the property FontSize. So my implementation of the GetError is quite complicated.

How can I deal with that behavior ? Did I do something wrong or is that a bug ?

Thanks a lot for your help