为什么要转换为Object来比较字符串？ [英] Why cast to Object to compare strings?
问题描述
为什么要将两个字符串转换为对象来比较它们？我在MSDN上的MS样本中看到了代码
但是没有得到它。
if（（object）name ==（object）attr。姓名）{
bothname和attr.name被声明为字符串。
http://msdn.microsoft.com/XML/Buildi...mlBkMkRead.asp
谢谢，
Sam
B-Line现在正在招聘一个华盛顿特区的VB.NET
开发者用于WinForms + WebServices位置。
中级到高级开发人员。对于
信息或将电子邮件简历应用于
sam_blinex_com。
" Samuel R. Neff" < BL **** @ newsgroup.nospam>在消息中写道
新闻：ia ******************************** @ 4ax.com ...
为什么要将两个字符串转换为对象来比较它们？我在MSDN上的MS示例中看到了代码
并且没有得到它。
if（（object）name ==（object）attr.name）{
<两者都是名称和attr.name声明为字符串。
绕过运算符重载。通过在这里转换为object，你
强制编译器使用objects == operator，这是一个参考
比较，而不是cast会使用strings == operator，
是字符串比较（字符比较的完整字符）。我不知道
特别是为什么作者觉得参考比较在这里很重要（我在你的例子中找不到
），但这就是效果。
我个人更喜欢使用object.ReferenceEquals（）而不是将
两个实例转换为对象。 http://msdn.microsoft.com/XML/Buildi...mlBkMkRead.asp
谢谢，
Sam
B-Line现在正在招聘一名华盛顿特区的VB.NET开发人员，负责WinForms + WebServices的职位。
中级到高级开发人员。有关
信息或将电子邮件简历应用于
sam_blinex_com。
谢谢，我没有意识到施放受影响的操作员超载
分辨率。
希望我知道为什么作者想要使用参考比较
$ b $但是，它很奇怪。
祝你好运，
Sam
星期二，22 2005年3月16:07:14 -0600，Daniel O''Connell [C＃MVP]"
< onyxkirx @ - NOSPAM--comcast.net>写道：
Samuel R. Neff < BL **** @ newsgroup.nospam>在消息中写道
新闻：ia ******************************** @ 4ax.com ..。< blockquote class =post_quotes>
为什么要将两个字符串转换为对象来比较它们？我在MSDN上的MS示例中看到了代码
并且没有得到它。
if（（object）name ==（object）attr.name）{
<两者都是名称和attr.name声明为字符串。
是绕过运算符重载。通过在这里转换为object，你强制编译器使用objects == operator，这是一个参考比较，而不是cast会使用strings == operator，这是一个字符串比较（完整字符与字符比较）。我不知道
具体为什么作者认为参考比较在这里很重要（我在你的例子中找不到它），但那就是效果。
我个人更喜欢使用object.ReferenceEquals（）而不是将两个实例转换为对象。http://msdn.microsoft.com/XML/Buildi .. .mlBkMkRead.asp
谢谢，
Sam
B-Line正在招聘一名华盛顿特区VB.NET
开发者为WinForms + WebServices职位。
中级到高级开发人员。对于
信息或将电子邮件简历应用于
sam_blinex_com。
是否使用character-by比较字符串 - 字符比较？由于
CLR执行字符串折叠，所以不是所有相同的字符串真的是
相同的副本吗？所以没有==对于字符串只是做一个参考
比较，因为它对对象呢？
我没有看到比较点
你知道所有对相同字符串的引用指向相同的
内存位置......
Why would you cast two strings to objects to compare them? I saw code
in an MS sample on MSDN and don''t get it.
if ( (object)name == (object)attr.name ) {
both "name" and "attr.name" are declared as string.
http://msdn.microsoft.com/XML/Buildi...mlBkMkRead.asp
Thanks,
Sam
B-Line is now hiring one Washington D.C. area VB.NET
developer for WinForms + WebServices position.
Seaking mid to senior level developer. For
information or to apply e-mail resume to
sam_blinex_com.
"Samuel R. Neff" <bl****@newsgroup.nospam> wrote in message
news:ia********************************@4ax.com...
Why would you cast two strings to objects to compare them? I saw code
in an MS sample on MSDN and don''t get it.
if ( (object)name == (object)attr.name ) {
both "name" and "attr.name" are declared as string.
It is to circumvent operator overloading. By casting to object here, you
force the compiler to use objects == operator, which is a reference
comparison, whereas not casting would have used strings == operator, which
is a string comparison(full character to character compare). I don''t know
specifically why the author felt reference comparison was important here(I
can''t find it in your example), but that is the effect.
I personally prefer to use object.ReferenceEquals() instead of casting the
two instances to object. http://msdn.microsoft.com/XML/Buildi...mlBkMkRead.asp
Thanks,
Sam
B-Line is now hiring one Washington D.C. area VB.NET
developer for WinForms + WebServices position.
Seaking mid to senior level developer. For
information or to apply e-mail resume to
sam_blinex_com.
Thanks, I didn''t realize casting affected operator overload
resolution.
Wish I knew why the writer wanted to use reference comparison for
strings though, it''s weird.
Best regards,
Sam
On Tue, 22 Mar 2005 16:07:14 -0600, "Daniel O''Connell [C# MVP]"
<onyxkirx@--NOSPAM--comcast.net> wrote:
"Samuel R. Neff" <bl****@newsgroup.nospam> wrote in message
news:ia********************************@4ax.com.. .
Why would you cast two strings to objects to compare them? I saw code
in an MS sample on MSDN and don''t get it.
if ( (object)name == (object)attr.name ) {
both "name" and "attr.name" are declared as string.
It is to circumvent operator overloading. By casting to object here, you
force the compiler to use objects == operator, which is a reference
comparison, whereas not casting would have used strings == operator, which
is a string comparison(full character to character compare). I don''t know
specifically why the author felt reference comparison was important here(I
can''t find it in your example), but that is the effect.
I personally prefer to use object.ReferenceEquals() instead of casting the
two instances to object.http://msdn.microsoft.com/XML/Buildi...mlBkMkRead.asp
Thanks,
Sam
B-Line is now hiring one Washington D.C. area VB.NET
developer for WinForms + WebServices position.
Seaking mid to senior level developer. For
information or to apply e-mail resume to
sam_blinex_com.
Are strings compared using character-by-character comparison? Since the
CLR performs string folding, aren''t all identical strings really the
same copy anyway? So doesn''t == for strings just do a reference
comparison as it does for object?
I don''t see the point of comparing strings character-by-character when
you know that all references to identical strings point to the same
memory location...?
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