Code Reference » null http://sullivan.net/blog A collection of code for my reference (and perhaps other people too) Wed, 25 Jan 2012 17:53:32 +0000 en hourly 1 http://wordpress.org/?v=3.2.1 Checking for null http://sullivan.net/blog/2009/08/checking-for-null/ http://sullivan.net/blog/2009/08/checking-for-null/#comments Fri, 14 Aug 2009 10:25:26 +0000 Darren http://sullivan.net/blog/?p=85 Checking for null is done differently in each langauge.

* In a string (C#):

if (string.IsNullOrEmpty(myString))
{ }

* In a database (T-SQL):

SELECT *
FROM [Customers]
WHERE Address IS NULL

* Database return value (C#):

if (myProperty == DBNull.Value)
{ }

* In Javascript:

if (myVariable == null)
{ }

* In Javascript - check if an object exists or has been created yet. This is different than checking for a null value:

if (typeof(jQuery) == 'undefined')
{ }

* In ASP:

if myVariable is null then 

end if

* In ASP - check if an object exists - example when receiving an XML object:

Set SourceObj = Server.CreateObject("MSXML2.DOMDocument.6.0")
SourceObj.async = false
SourceObj.setProperty "SelectionLanguage", "XPath"
SourceObj.loadXML( xmlhttp.responseText )

uid = SourceObj.documentElement.selectSingleNode("//sessionId")
if uid is nothing then
   uid = "n.a."
else
   uid = uid.text
end if

* In PHP:


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