vb.net - VB setting a string to nothing -

-

this question has answer here:

the code below returns true when expected return false.

why return true? expect nothing set value of string null, not empty (according msdn)

codeingground sample

module vbmodule      sub main()         dim x string         x = nothing         console.writeline(x = string.empty)     end sub  end module

nothing (visual basic)

represents default value of data type. reference types, default value null reference.

***edit**** nothing = string.empty (why these equal?)

nothing in vb.net default value type. language spec says in section 2.4.7:

nothing special literal; not have type , convertible types in type system, including type parameters. when converted particular type, equivalent of default value of type.

so, when test against string.empty, nothing converted string, has length 0. operator should used testing against nothing, , string.empty.equals(nothing) return false.

per comment,

when converted particular type, equivalent of default value of type.

the default value string null. dont understand why answer accepted.

difference between c# , vb.net string comparison

the above post explains answer clearly, credit goes tim schmelter in comment section finding above post

per tim schmeleters comments

it called vb compiler documentation states in string.equality operator


Comments

Post a Comment

Popular posts from this blog

Fail to load namespace Spring Security http://www.springframework.org/security/tags -

-
i have problem namespace of spring security on xhtml page. don't understand why can't load uri, , have following issue: whitelabel error page application has no explicit mapping /error, seeing fallback. tue jul 21 16:58:12 utc 2015 there unexpected error (type=not found, status=404). please need help! possible uri has been changed? best regards you using incorrect namespace url. correct url http://www.springframework.org/schema/security the error page seeing spring source website since not recognize url. try visiting http://www.springsource.org/security/tags in browser update : spring security tags used in jsp page correct tag lib declaration is: <%@ taglib prefix="sec" uri="http://www.springframework.org/security/tags" %>
Read more

sql - MySQL query optimization using coalesce -

-
can explain me why second query faster first? (first 1 takes around 40 seconds, second 1 less 0.1) select releases.feature_code, releases.platform_id, version, release_date, general_available, uri, filesize, display_name, feature_name.full_name, if ((select exists(select 1 release_exceptions releases.feature_code = release_exceptions.feature_code , releases.platform_id = release_exceptions.platform_id , releases.version = release_exceptions.version) = 1), 1, 0) release_exceptions releases left outer join platform using(platform_id) left outer join feature_name using(feature_code) order version desc; ~~~ query 2 ------------------ ~~~ select feature_code, version, release_date, general_available, platform_id, uri, filesize, display_name, feature_name.full_name, coalesce(release_exceptions, 0) release_exceptions mus.releases left outer join ( select distinct feature_code, version, platform_id, 1 release_exceptions mus.release_exceptions ) release_exceptions using ...
Read more

unity3d - Unity local avoidance in user created world -

-
i'm using unity3d networked multiplayer online game have large complex 3d terrain scene forest, trees, cliff, hills, mountains, bounders, etc. players can build structures sort of minecraft, , put them anywhere in scene, or move them around anytime. aside human controlled players, there automated ai players , objects animals roaming around scene following path. the problem how make these automated ai players , animals, able navigate around static , dynamic player created structures, because path follow can blocked player created structures, or other players , other ai objects, cliffs etc. have find away around them or on track if tumble down off high cliff example. so made navmesh , used navagents, takes care of static, non moving objects, how make ai players navigate around each other , dynamic structures created players can number in hundreds? i thought of adding navmeshobstacle everything, result in being attached hundreds of objects since user created structures b...
Read more