[Mono-bugs] [Bug 579824] New: DataTable.Select comparisons resulting in "NULL<>" return TRUE instead of FALSE

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http://bugzilla.novell.com/show_bug.cgi?id=579824

http://bugzilla.novell.com/show_bug.cgi?id=579824#c0


           Summary: DataTable.Select comparisons resulting in "NULL<>"
                    return TRUE instead of FALSE
    Classification: Mono
           Product: Mono: Class Libraries
           Version: 2.4.x
          Platform: Other
        OS/Version: openSUSE 11.1
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: Sys.Data
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: janvanderwatt at gmail.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---
           Blocker: ---


Created an attachment (id=342358)
 --> (http://bugzilla.novell.com/attachment.cgi?id=342358)
Source code to test with

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2)
Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729)

When a filter expression uses the NOT EQUAL operator on a column, rows with
NULL in that column should not be returned, but they are returned on Mono.

(NULL here is shorthand for DBNull.Value, not the keyword "null")

Reproducible: Always

Steps to Reproduce:
1. Create a datatable with columns "Name" (String) and "Subscribed" (Boolean)
2. Set some "Names" to valid values, leave some NULL.
3. Set some "Subscribed" to false, leave some NULL (don't use TRUE as this
confuses the issue).
4. View the results of datatable.Select("Name<>'anything'").
5. View the results of datatable.Select("Subscribed<>False").
Actual Results:  
4. Rows with Name=NULL are also returned
5. Rows with Subscribed=NULL are also returned

Expected Results:  
4. Only rows with Name=<actual text, or empty string> to be returned
5. Only rows with Subscribed=True to be returned

i.e. if the operation is <> and any of the operands is NULL, the expression
should evaluate to false

(even "Name<>Null" is FALSE and should NOT return the rows where the name is
NULL - the correct expression for this is "Name Is Not Null")
(Mono throws an exception "Expression 'Subscribed<>Null' is invalid", but .NET
doesn't)

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