c# - Unable to cast object of type 'System.DateTime' to type 'System.String' -

-

getting error has me stumped. i'm assuming it's simple can't seem figure 1 out, code causing error:

if ((string) _nullabledatetimepicker1.value != string.empty && _nullabledatetimepicker1.value != null) {      _nullabledatetimepicker1.value = null; }

when clicking on search button in windows form, popping up:

unable cast object of type 'system.datetime' type 'system.string'.

it appears type of nullable-type instance of _nullabledatetimepicker1 datetime, not string; need compare datetime or convert string.

so, in simplest sense:

_nullabledatetimepicker1.value.tostring() != string.empty

however, beware danger of not checking hasvalue, cause nullreferenceexception if value null; so, check little backwards.

and then, if wasn't null, you'd have datetime.minvalue, , tostring wouldn't return empty string. therefore, check null on nullable thing, , if not null, compare datetime.minvalue (unless there's quirk in code means have different 'default'.


Popular posts from this blog

Php - Delimiter must not be alphanumeric or backslash -

-
this question has answer here: delimiter must not alphanumeric or backslash , preg_match 5 answers this question has been asked don't know how fix problem in situation. getting following php errror: php message: php warning: preg_match(): delimiter must not alphanumeric or backslash in... on line 227 line 227 following: if (preg_match($match, $_server['http_user_agent'])) and function: $oslist = array ( 'windows 3.11' => 'win16', 'windows 95' => '(windows 95)|(win95)|(windows_95)', 'windows 98' => '(windows 98)|(win98)', 'windows 2000' => '(windows nt 5.0)|(windows 2000)', 'windows xp' => '(windows nt 5.1)|(windows xp)', 'windows server 2003' => '(windows nt 5.2)', 'windows vista' => '(windows nt 6.0)', 'w...
Read more

Delphi interface implements -

-
i expect reference counting should work on outer aggregating object in interface implementation. if can refer example: clarity in classes implementing multiple interfaces (alternative delegation): here minimal reproduction of behaviour: program so16210993; {$apptype console} type ifoo = interface procedure foo; end; tfooimpl = class(tinterfacedobject, ifoo) procedure foo; end; tcontainer = class(tinterfacedobject, ifoo) private ffoo: ifoo; public constructor create; destructor destroy; override; property foo: ifoo read ffoo implements ifoo; end; procedure tfooimpl.foo; begin writeln('tfooimpl.foo called'); end; constructor tcontainer.create; begin inherited; ffoo := tfooimpl.create; end; destructor tcontainer.destroy; begin writeln('tcontainer.destroy called');//this line never runs inherited; end; procedure main; var foo : ifoo; begin foo := tcontainer.create; foo.foo; end; begin main; readln...
Read more

css - invalid property value for padding -

-
i getting invalid property value padding , don't know why. code written in ruby btw. when check browser has right value pixels, crossed out w line , isn't reading attribute. in advance. <% mywaldo = mapping::mywaldos.sample %> <!doctype html> <html> <head> <title>sinatra single-serve</title> <link href="css/bootstrap.css" rel="stylesheet" type="text/css"/> <style> div { width: 1024px; height: 768px; background-image: url("img/waldos/<%= mywaldo[0]%>") ; } #waldo { position:absolute; top: <%= mywaldo[2]%>; left: <%= mywaldo[1]%>; padding: <%= mywaldo[3]%>, <%= mywaldo[4]%>; } </style> </head> <body> <div> <a id="waldo" href="">aa</a> </div> <%= yield %> </body> ...
Read more