Just as a slight cosmetic addition to Rune’s suggestion, you could create your own extension method: public static IEnumerable<T> OrEmptyIfNull<T>(this IEnumerable<T> source) { return source ?? Enumerable.Empty<T>(); } Then you can write: foreach (var header in file.Headers.OrEmptyIfNull()) { } Change the name according to taste 🙂
If the sent_at field is not there when its not set then: db.emails.count({sent_at: {$exists: false}}) If it’s there and null, or not there at all: db.emails.count({sent_at: null}) If it’s there and null: db.emails.count({sent_at: { $type: 10 }}) The Query for Null or Missing Fields section of the MongoDB manual describes how to query for null … Read more
The issue is that String.valueOf method is overloaded: String.valueOf(Object) String.valueOf(char[]) Java Specification Language mandates that in these kind of cases, the most specific overload is chosen: JLS 15.12.2.5 Choosing the Most Specific Method If more than one member method is both accessible and applicable to a method invocation, it is necessary to choose one to … Read more
If the field is fixed width storing NULL takes the same space as any other value – the width of the field. If the field is variable width the NULL value takes up no space. In addition to the space required to store a null value there is also an overhead for having a nullable … Read more
The rationale behind not returning null is that you do not have to check for it and hence your code does not need to follow a different path based on the return value. You might want to check out the Null Object Pattern which provides more information on this. For example, if I were to … Read more
They’re two completely different things. == compares the object reference, if any, contained by a variable. .equals() checks to see if two objects are equal according to their contract for what equality means. It’s entirely possible for two distinct object instances to be “equal” according to their contract. And then there’s the minor detail that … Read more
7.20.3.2 The free function Synopsis #include <stdlib.h> void free(void *ptr); Description The free function causes the space pointed to by ptr to be deallocated, that is, made available for further allocation. If ptr is a null pointer, no action occurs. See ISO-IEC 9899. That being said, when looking at different codebases in the wild, you’ll … Read more
ALTER TABLE person ALTER COLUMN phone DROP NOT NULL; More details in the manual: http://www.postgresql.org/docs/9.1/static/sql-altertable.html
Update: The Roslyn compiler has been updated to make the behavior of the two operators the same when there is no overloaded equality operator. Please see the code in the current compiler results (M1 and M2 in the code) that shows what happens when there is no overloaded equality comparer. They both now have the … Read more
Undefined typically refers to something which has not yet been assigned a value (yet). Null refers to something which definitively has no value. In that case, I would recommend returning a null. Note that a function with no specified return value implicitly returns undefined. From the ECMAScript2015 spec 4.3.10 undefined value primitive value used when … Read more