铸造VS转换对象的toString，当物体确实是一个字符串 [英] Casting vs Converting an object toString, when object really is a string

问题描述

这是不是一个真正的问题，但是我很好奇。当我保存一个字符串中可以说一个的DataRow，它被转换为对象。当我想用它，我一定要投它的ToString。据我知道有这样做的几种方法，第一个是

 字符串名称=（字符串）DataRowObject [名称]; //有效的，因为我知道这是一个字符串
 

和另一个是：

 字符串名称= DataRowObject [名称]的ToString（）。
 

我感兴趣的是在两者之间有什么区别？是第一个更有效率？ （这只是一种炒作，在我的脑海ToString（）方法是通过一些循环机制，即只有投它可能会更快实现，然而，这只是一种直觉我有）。

时甚至有这样做的更快/更优雅的方式？

任何人都可以清除此为我？

解决方案

  

两个旨在用于不同
  目的。任何ToString方法
  对象应该返回字符串
  再这个对象的presentation。铸件
  是完全不同的，而'为'键
  词在一定条件下转换，如
  已经说了。在'为'关键字
  基本上说给我拿的参考
  这种类型的到该对象，如果该
  对象是这种类型的ToString时
  说给我一个重新串presentation
  该对象的，其结果可能是
  同样在某些情况下，但两者应该
  从未被认为可互换
  因为，正如我所说，他们的存在
  不同的目的。如果你的意图
  是投那么你应该总是使用
  铸造，NOT的ToString。

从<一个href=\"http://www.$c$cguru.com/forum/showthread.php?t=443873\">http://www.$c$cguru.com/forum/showthread.php?t=443873

又见<一个href=\"http://bytes.com/groups/net-c/225365-tostring-string-cast\">http://bytes.com/groups/net-c/225365-tostring-string-cast

This isn't really an issue, however I am curious. When I save a string in lets say an DataRow, it is cast to Object. When I want to use it, I have to cast it ToString. As far as I know there are several ways of doing this, first is

string name = (string)DataRowObject["name"]; //valid since I know it's a string

and another one is:

string name = DataRowObject["name"].ToString();

I am interested in what is the difference between both? Is the first more efficient? (This is just a speculation, in my head ToString() method is implemented by some looping mechanism where just casting it "could" be faster, however this is just a "gut feeling" I have).

Is there even a faster / more elegant way of doing this?

Can anyone clear this up for me?

解决方案

The two are intended for different purposes. The ToString method of any object is supposed to return a string representation of that object. Casting is quite different, and the 'as' key word performs a conditional cast, as has been said. The 'as' key word basically says "get me a reference of this type to that object if that object is this type" while ToString says "get me a string representation of that object". The result may be the same in some cases but the two should never be considered interchangeable because, as I said, they exist for different purposes. If your intention is to cast then you should always use a cast, NOT ToString.

from http://www.codeguru.com/forum/showthread.php?t=443873

see also http://bytes.com/groups/net-c/225365-tostring-string-cast

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