Lambda expression with and System.Nullable

Question

This can't compile:

void Foo()
{
    using (var db = new BarDataContext(ConnectionString))
    {
        // baz is type 'bool'
        // bazNullable is type 'System.Nullable<bool>'
        var list = db.Bars.Where(p => p.baz && p.bazNullable); // Compiler: 
            // Cannot apply operator '&&' to operands of type
            // 'System.Nullable<bool> and 'bool'
    }
}

Do I really have to make this through two runs, where I first use the as condition and then run through that list with the nullable conditions, or is there a better clean smooth best practice way to do this?

score 8 · Accepted Answer · answered Jul 08 '11 at 09:27

8

p.bazNullable.GetValueOrDefault()

answered Jul 08 '11 at 09:27

gsharp

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+1 for this one. nice. i didn't know there is a `GetValueOrDefault`. – Cheng Chen Jul 08 '11 at 09:28
I couldn't use `GetValueOrDefault` in a LINQ query, but explicitly adding `== true` worked. – Vivelin Jan 13 '14 at 11:31
You can pass a default value as well like this in GetValueOrDefault(false). It will return false if the bool contains null value. Helped me tremendously in LINQ where clauses. – Fahad Abid Janjua Jul 05 '16 at 01:23

score 5 · Answer 2 · answered Jul 08 '11 at 09:26

5

Something like this?

 db.Bars.Where(p => p.baz && p.bazNullable.HasValue && p.bazNullable.Value);

I don't know if Linq-to-Sql can handle it.

answered Jul 08 '11 at 09:26

Stefan Steinegger

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score 4 · Answer 3 · edited May 23 '17 at 10:28

There are two issues here:

The shortcircuiting && is not supported on nullable types for some reason. (Related Why are there no lifted short-circuiting operators on `bool?`?)

The second is that even if it were supported by C#, your code still makes no sense. Where needs a bool as result type of your condition, not a bool?. So you need to decide how the case where baz==true and bazNullable==null should be treated.

This leads to either p.baz && (p.bazNullable==true) or p.baz && (p.bazNullable!=false) depending on what you want.

Or alternatively p.baz && (p.bazNullable??false) or p.baz && (p.bazNullable??true)

score 1 · Answer 4 · answered Jul 08 '11 at 09:28

You're trying to apply a logical && operation to a nullable bool.

If you are sure that p.bazNullable is not null, then you can try

var list = db.Bars.Where(p => p.baz && p.bazNullable.Value);

or if a null value equates to false, then try

var list = db.Bars.Where(p => p.baz && p.bazNullable.ValueOrDefault(false));

Saeed Neamati · Answer 5 · 2011-07-08T09:34:04.093

0

use:

  var list = db.Bars.Where(p => p.baz && p.bazNullable.Value);

To handle null exceptions use:

  var list = db.Bars.Where(p => p.baz && p.bazNullable != null && p.bazNullable.Value);

edited Jul 08 '11 at 09:34

answered Jul 08 '11 at 09:27

Saeed Neamati

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score 0 · Answer 6 · answered Jul 08 '11 at 09:28

0

you could just do:

var list = db.Bars.Where(p => p.baz && p.bazNullable != null && p.bazNullable == true);

answered Jul 08 '11 at 09:28

ub1k

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Checking `HasValue` is a lot simpler, but that could also work. – Alex R. Jul 08 '11 at 09:30

V4Vendetta · Answer 7 · 2011-07-08T10:02:00.837

0

How about this

Where(p => p.baz && (p.bazNullable ?? false));

OR

Where(p => p.baz && (p.bazNullable ==null ? false : p.bazNullable.Value));

edited Jul 08 '11 at 10:02

answered Jul 08 '11 at 09:49

V4Vendetta

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Might it be safer to use nullable HasValue instead of checking for just nulls? Example: Where(p => p.baz && (p.bazNullable.HasValue && p.bazNullable.Value)); – Ben Clark-Robinson Aug 02 '11 at 07:12

Lambda expression with and System.Nullable

7 Answers7