？和：用于v2中的条件表达式 [英] ? and : for conditional expressions in v2
问题描述
在v1.x中，以下代码完美运行：
mobjSqlParameter.Value = strPayerBusinessName == null？ strPayerBusinessName
:(对象）DBNull.Value;
但是，我无法在v2中使用它。我知道
strPayerBusinessName的值为null，因为如果我在立即窗口中写了
strPayerBusinessName == null，它将返回true。
但是，表达式似乎没有评估右侧，没有
我写的东西。例如，以下代码
mobjSqlParameter.Value = strPayerBusinessName == null？ strPayerBusinessName
：" Hello" ;;
不会使用字符串Hello填充mobjSqlParameter.Value。什么时候
strPayerBusinessName为空。
这个语法在v2中是否被弃用？
当然我意识到，我可以写：
if（strPayerBusinessName == null）
{
mobjSqlParameter.Value = DBNull.Value;
}
其他
{
mobjSqlParameter.Value = strPayerBusinessName;
}
但我很好奇为什么？ ：语法似乎不再起作用了。
感激不尽的任何帮助。
Mark
Hi,
In v1.x, the following code worked perfectly:
mobjSqlParameter.Value = strPayerBusinessName == null ? strPayerBusinessName
: (object)DBNull.Value;
However, I can''t get it to work in v2. I know that the value of
strPayerBusinessName is null because if I write
strPayerBusinessName == null in the Immediate Window, it returns "true".
However, the expression does not seem to evaluate the right-hand side, no
matter what I write. E.g., the following code
mobjSqlParameter.Value = strPayerBusinessName == null ? strPayerBusinessName
: "Hello";
does not populate mobjSqlParameter.Value with the string "Hello" when
strPayerBusinessName is null.
Has this syntax been deprecated in v2?
I realise, of course, that I can write:
if(strPayerBusinessName == null)
{
mobjSqlParameter.Value = DBNull.Value;
}
else
{
mobjSqlParameter.Value = strPayerBusinessName;
}
but I''m curious as to why the ? : syntax doesn''t seem to work any more.
Any assistance gratefully received.
Mark
推荐答案
？：工作原理与以往一样，但是你注意到你使用了
错误的比较吗？当名字为空时你正在返回名字，而我不会认为这是你打算做的！使用！=代替==或
否则反转：分支。
-
http://www.kynosarges.de
?: works the same as ever, but did you notice that you''re using the
wrong comparison? You''re returning Name when Name is null, and I
don''t think that''s what you intend to do! Use != instead of == or
else reverse the : branches.
--
http://www.kynosarges.de
Mark Rae< ma ** @ markN- OSPAM.co.uk>写道：
Mark Rae <ma**@markN-O-S-P-A-M.co.uk> wrote:
在v1.x中，以下代码完美运行：
mobjSqlParameter.Value = strPayerBusinessName == null？ strPayerBusinessName
:(对象）DBNull.Value;
然而，我无法在v2中使用它。我知道
strPayerBusinessName的值为null，因为如果我在立即窗口中写了
strPayerBusinessName == null，它将返回true。
然而，表达似乎没有评估右侧，不是我写的东西。例如，以下代码
mobjSqlParameter.Value = strPayerBusinessName == null？ strPayerBusinessName
：" Hello";
不会使用字符串Hello填充mobjSqlParameter.Value。当
strPayerBusinessName为null时。
v2中是否已弃用此语法？
In v1.x, the following code worked perfectly:
mobjSqlParameter.Value = strPayerBusinessName == null ? strPayerBusinessName
: (object)DBNull.Value;
However, I can''t get it to work in v2. I know that the value of
strPayerBusinessName is null because if I write
strPayerBusinessName == null in the Immediate Window, it returns "true".
However, the expression does not seem to evaluate the right-hand side, no
matter what I write. E.g., the following code
mobjSqlParameter.Value = strPayerBusinessName == null ? strPayerBusinessName
: "Hello";
does not populate mobjSqlParameter.Value with the string "Hello" when
strPayerBusinessName is null.
Has this syntax been deprecated in v2?
否。我怀疑其他内容正在发生。
你能发一个简短但完整的程序来演示
的问题吗？
见 http://www.pobox.com/~skeet/csharp/complete.html 有关详细信息
我的意思是什么。
您可能对null合并运算符感兴趣，但是，
会让你这样做：
mobjSqlParameter.Value = strPayerBusinessName ?? 你好;
见 http://www.pobox.com/~skeet/csharp/c.../nullable.html 了解更多
详情。
-
Jon Skeet - < sk *** @ pobox.com>
http://www.pobox.com/~skeet 博客： http://www.msmvps.com/jon.skeet
如果回复该群组，请不要给我发邮件
No. I suspect something else is going on.
Could you post a short but complete program which demonstrates the
problem?
See http://www.pobox.com/~skeet/csharp/complete.html for details of
what I mean by that.
You might be interested in the null coalescing operator, however, which
would let you do:
mobjSqlParameter.Value = strPayerBusinessName ?? "Hello";
See http://www.pobox.com/~skeet/csharp/c.../nullable.html for more
details.
--
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
" Jon Skeet [C＃MVP]" < SK *** @ pobox.com>在消息中写道
新闻：MP ************************ @ msnews.microsoft.c om ...
"Jon Skeet [C# MVP]" <sk***@pobox.com> wrote in message
news:MP************************@msnews.microsoft.c om...
您可能对null合并运算符感兴趣，但是，它可以让您这样做：
mobjSqlParameter.Value = strPayerBusinessName ?? "你好英寸;
完美！非常感谢，Jon一如既往！
参见 http://www.pobox.com/~skeet/csharp/c.../nullable.html 了解更多详情。
You might be interested in the null coalescing operator, however, which
would let you do:
mobjSqlParameter.Value = strPayerBusinessName ?? "Hello";
Perfect! Thanks a lot, Jon, as always!
See http://www.pobox.com/~skeet/csharp/c.../nullable.html for more
details.
非常有用！
Incredibly useful!
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