Bug 58018 - Concatenating null strings leads to incorrect results
Summary: Concatenating null strings leads to incorrect results
Status: RESOLVED FIXED
Alias: None
Product: Workbooks & Inspector
Classification: Xamarin
Component: Actually Unsure ()
Version: master
Hardware: PC Mac OS
: --- normal
Target Milestone: ---
Assignee: xamarininteractive
URL:
Depends on:
Blocks:
 
Reported: 2017-07-07 21:13 UTC by Larry O'Brien
Modified: 2017-08-21 17:28 UTC (History)
2 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:


Attachments
Workbook demonstrating behavior (707 bytes, text/plain)
2017-07-07 21:13 UTC, Larry O'Brien
Details


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Status:
RESOLVED FIXED

Description Larry O'Brien 2017-07-07 21:13:55 UTC
Created attachment 23413 [details]
Workbook demonstrating behavior

Evaluating `((string) null) + ( (string) null)` in Workbooks shows an evaluation of `null`, but it should evaluate to an empty string (""). Also:

var s = (string)null;
"" + s;

evaluates to `null` but should evaluate to `""`. 

FWIW, "A" + s evaluates properly to "A" 


According to "https://github.com/dotnet/csharplang/blob/master/spec/expressions.md#arithmetic-operators" 

"These overloads of the binary + operator perform string concatenation. If an operand of string concatenation is null, an empty string is substituted. Otherwise, any non-string argument is converted to its string representation by invoking the virtual ToString method inherited from type object. If ToString returns null, an empty string is substituted."