score:12

Accepted answer

You can only compare an int to NULL if the int is nullable. If not, the default value for int will be 0 and never null.

You define a nullable int property like this:

int? value { get; set; }

And check it like this:

if ( value != null )
{
   int x = value.Value;
}

In the where clause of a Linq query it would be

var result = from d in data
             where d.Value != null
             select d

score:7

If you are comparing to a null value, you must first compare your value to null due to a bug.

var field = from field in table
            where (value == null ? field.property == null : field.property == value)
            select field;

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