I have table with nullable fields :

```
public int? Order {get; set;}
public DateTime? StartDate {get; set;}
public DateTime? EndDate {get; set;}
public string Text {get; set;}

```

All this fields can be with NULL value

Problem starts when I want to query records 

* where Order, StartDate, EndDate and Text aren't NULL or
* where Order, StartDate and Text aren't null but EndDate is null or
* where Order and Text aren't null but StartDate and EndDate are null

`Order.HasValue && StartDate.HasValue && EndDate.HasValue && !string.IsNullOrEmpty(Text) || Order.HasValue && StartDate.HasValue && !EndDate.HasValue && !string.IsNullOrEmpty(Text) || Order.HasValue && !StartDate.HasValue && !EndDate.HasValue && !string.IsNullOrEmpty(Text)`

Using such query I get error or 400 (bad request) or unsupported operator (isnullorempty isn't supported)

According to this answer <https://stackoverflow.com/a/4263091/3917754> it is impossible to query NULL values...