gistfile1.cs

    public static class MontaFiltro<T, P>
        where P : DbParameter, new()
    {
        public static string RetornaWhere(T obj, out List<P> parameters)
        {
            parameters = new List<P>();
            var where = new List<string>();

            foreach (var property in obj.GetType().GetProperties())
            {
                var tableFilter = GetAttributeFrom(property);
                var valor = GetValueFrom(obj, property);

                if (HasNoValue(valor) || MustBeIgnored(tableFilter, valor) || ValueIsEmptyDateTime(property, valor))
                    continue;

                if (IsDateTimeLast(property, tableFilter))
                    valor = AddAlmostOneDayTo(valor);

                if (tableFilter.IsLikeCommand)
                    valor = "%" + valor + "%";

                where.Add(string.Format("{0}.{1} {2} :{3}", tableFilter.TableName, tableFilter.ColumnName, tableFilter.Operacao, tableFilter.ParamName));

                AddParameterTo(parameters, tableFilter, valor);
            }

            if (where.Any()) 
                return string.Join(" AND ", where.ToArray())
            else 
                return string.Empty;
        }

        private static void AddParameterTo(List<P> parameters, TableFilter tableFilter, object valor)
        {
            parameters.Add(new P { ParameterName = ":" + tableFilter.ParamName, Value = valor });
        }

        private static object AddAlmostOneDayTo(object valor)
        {
            var dateTime = Convert.ToDateTime(valor);
            valor = dateTime.AddHours(23).AddMinutes(59).AddSeconds(59);
            return valor;
        }

        private static bool IsDateTimeLast(System.Reflection.PropertyInfo property, TableFilter tableFilter)
        {
            return property.PropertyType.Equals(typeof(DateTime)) && tableFilter.IsDataTimeLast;
        }

        private static bool ValueIsEmptyDateTime(System.Reflection.PropertyInfo property, object valor)
        {
            return property.PropertyType.Equals(typeof(DateTime)) && valor.Equals(DateTime.MinValue);
        }

        private static bool MustBeIgnored(TableFilter tableFilter, object valor)
        {
            return !string.IsNullOrEmpty(tableFilter.IgnoreValue) && valor.ToString().Equals(tableFilter.IgnoreValue);
        }

        private static bool HasNoValue(object valor)
        {
            return valor == null || string.IsNullOrEmpty(valor.ToString());
        }

        private static object GetValueFrom(T obj, System.Reflection.PropertyInfo property)
        {
            var valor = property.GetValue(obj, null);
            return valor;
        }

        private static TableFilter GetAttributeFrom(System.Reflection.PropertyInfo property)
        {
            var tableFilter = property.GetCustomAttributes(typeof(TableFilter), false)[0] as TableFilter;
            return tableFilter;
        }
    }