Null checking inside where clause in Entity Framework Linq

Question

I have a query that returns null reference exception. I'm filter data using searching, I put breakpoint and check that the problem is that when a column has a null value it returns exception.

Controller:

if (searchValue != null || searchValue != "")
{
     expheadlist = expheadlist.Where(e => 
                    e.Name.ToLower().Contains(searchValue) || 
                    e.Description.ToLower().Contains(searchValue) 
                    ).ToList<GenExpenseHead>();
}

I allowed null values in Description attribute. This entity has a null value in Description column. I think therefore it returns NullException in this code. I don't know how to resolve it.

Thanks in Advance.

Use ...`e.Description?.ToLower`... the db can handle nulls, but c# can't call method on null reference. But it looks, that this is executed as linq to objects and not ef linq, should see how the source of this qury us prepared. — ZorgoZ, Dec 26 '18 at 07:56

TanvirArjel · Accepted Answer · 2018-12-26T08:53:26.887

5

You cannot write ?. (null conditional operator) and ?? (null coalescing operator) in Where clause. Instead use string.IsNullOrWhiteSpace in your query as follows:

if (!String.IsNullOrWhiteSpace(searchValue))
{
     expheadlist = expheadlist.Where(e => (string.IsNullOrWhiteSpace(e.Name) || e.Name.ToLower().Contains(searchValue))
                    || (string.IsNullOrWhiteSpace(e.Description) || e.Description.ToLower().Contains(searchValue))
                    ).ToList<GenExpenseHead>();
}

Moreover also simply your searchValue != null || searchValue != "" condition using string.IsNullOrWhiteSpace as I have used!

edited Dec 26 '18 at 08:53

answered Dec 26 '18 at 08:06

TanvirArjel

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Has it worked for you? – TanvirArjel Dec 26 '18 at 08:26
What is the error showing it right now? – TanvirArjel Dec 26 '18 at 08:27
`only, call, increment, decrement, await and new object expressions can be used as a statement.` – Huzaifa Dec 26 '18 at 08:29
Try removing the `?? false` from the `Name` and `Description` and let me know if it works? – TanvirArjel Dec 26 '18 at 08:31
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/185775/discussion-between-huzaifa-and-tanvirarjel). – Huzaifa Dec 26 '18 at 08:34

score 1 · Answer 2 · answered Dec 26 '18 at 07:54

1

one way to solve it would be using the ?. (null propagation operator) and ?? (null coalescing operator):

expheadlist = expheadlist.Where(e => 
                    e.Name.ToLower().Contains(searchValue) || 
                    e.Description?.ToLower().Contains(searchValue) ?? false
                    ).ToList<GenExpenseHead>();

This says if Description is null then return false preventing the exception otherwise call .ToLower().Contains(searchValue)

answered Dec 26 '18 at 07:54

Ousmane D.

54,915
8
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1

You cannot write `?.` (null conditional operator) and `??` (null coalescing operator) in `Where` clause as you wrote. it will throw `only, call, increment, decrement, await and new object expressions can be used as a statement.` error. – TanvirArjel Dec 26 '18 at 08:42

score 0 · Answer 3 · answered Dec 26 '18 at 08:01

using ?. (null propagation operator) and ?? (null coalescing operator) for both fields such as

expheadlist = expheadlist.Where(e => 
                e.Name?.ToLower().Contains(searchValue) ?? false || 
                e.Description?.ToLower().Contains(searchValue) ?? false
                ).ToList<GenExpenseHead>();

Null checking inside where clause in Entity Framework Linq

3 Answers3