stringOperand + null = ?

[Mark Chambers]

Hi there,

In the expression A + B where A is a string and B isn't, I know that
"B.ToString()" will be called and the results concatenated. If B is null
however does the standard guarantee that "String.Empty" will be used
instead. Thanks.

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Mark Chambers wrote:

Hi there,

In the expression A + B where A is a string and B isn't, I know that
"B.ToString()" will be called and the results concatenated. If B is null
however does the standard guarantee that "String.Empty" will be used
instead. Thanks.

The + operator uses the String.Concat method.

From the specification of the String.Concat method:

"An Empty string is used in place of any null argument."

--
Göran Andersson
_____
http://www.guffa.com

[Mark Chambers]

>Hi there,

>>
In the expression A + B where A is a string and B isn't, I know that
"B.ToString()" will be called and the results concatenated. If B is null
however does the standard guarantee that "String.Empty" will be used
instead. Thanks.

The + operator uses the String.Concat method.

From the specification of the String.Concat method:

"An Empty string is used in place of any null argument."

Thanks. I didn't know it defers to "String.Concat()".

[Jon Skeet [C# MVP]]

Mark Chambers <no_spam@_nospam.comwrote:

Hi there,

In the expression A + B where A is a string and B isn't, I know that
"B.ToString()" will be called and the results concatenated. If B is null
however does the standard guarantee that "String.Empty" will be used
instead. Thanks.

Yup, the spec says:

<quote>
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.
</quote>

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[Mark Chambers]

Yup, the spec says:

>
<quote>
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.
</quote>

Thanks for the confirmation. Appreciated.