正确的C＃转换为对应的VB的CTYPE（） [英] Correct C# conversion counterpart for VB's CTYPE()

问题描述

以下是从VB，我移植到C＃重写一个片段。我的问题是什么是 receipt_date 在转让之后？是不是仍然是一个对象或者是一个字符串？

The below is a snippet from VB that I am porting to a C# rewrite. My question is what is receipt_date after the assignment? Is it still an object or is it a string?

Dim receipt_date As Object
receipt_date = CType(dr.Item("RECTDT"), String)

这会是正确的C＃同行？

Would this be the correct C# counterpart?

object receipt_date;
receipt_date = dr["RECTDT"].ToString();

在这两种执行将在 VB 版本， receipt_date 等于 C＃版本？如果没有，你有什么我需要做，使会这样呢？谢谢

After both of these execute would the VB version, receipt_date be equal to the C# version? If not, what do I need to do to make it so? Thanks

推荐答案

是的，你最终会得到相同的结果。它，而不是使用VB的版本（你调用的ToString（）语义不同的明确 CTYPE ，这是松散相当于投在C＃中），但它的功能相同。这也是比较安全的，因为在数据库中铸造一个空值（这将是的DBNull 在运行时）会抛出异常。

Yes, you would end up with the same result. It's semantically different from the VB version (you're calling ToString() explicitly instead of using CType, which is loosely equivalent to a cast in C#), but it's functionally identical. It's also safer, since casting a null value in the database (which would be DBNull in the runtime) would throw an exception.

贪图的是COM prehensive，不过，实际的C＃对应的是这样的：

Just for the sake of being comprehensive, though, the actual C# counterpart would be this:

var receipt_date = (string)dr["RECTDT"];

作为一个点的风格，但是，尽量避免隐式类型（例如，使用称 VAR 关键字，而不是字符串或 INT ）的简单类型。 VAR 当类型可能会在未来改变是很有用的（而且并不重要），或者如果类型是长期和/或复杂的变种使其更具可读性。在这种情况下，我建议：

As a point of style, though, try to avoid implicit typing (i.e., using the var keyword instead of saying string or int) for simple types. var is useful when the type might change in the future (and isn't important), or if the type is long and/or complex and var makes it more readable. In this instance, I would suggest:

string receipt_date = (string)dr["RECTDT"];

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