将DateTime转换为ShortDateString时出错？ [英] Error while converting DateTime to ShortDateString?

问题描述

我可以使用这一行将DateTime转换为ShortDateString。

I can convert the DateTime to ShortDateString using this line.

li.SubItems.Add(CType(dt.Rows(i).Item("student_dob"), DateTime).ToShortDateString)

但下一行是错误的。为什么？请提供解决方案。

But this next line is giving an error. Why? Please provide a solution.

li.SubItems.Add(CType(("student_dob"), DateTime).ToShortDateString)

错误是：从字符串student_dob到日期类型的转换无效。

The error is: Conversion from string "student_dob" to type 'Date' is not valid.

推荐答案

你得到那个错误，因为你试图将字符串student_dob字面转换为DateTime。这是不可能的，因为它根本不是有效日期。首先必须获取要转换的项目，就像在第一个代码块中一样。

You get that error because you are trying to convert the string "student_dob" literally to a DateTime. This is not possible because it is not a valid date at all. You first have to fetch the item to convert, like you did in your first code block.

让我们试着看看发生了什么：

该行试图将项目添加到可能是ListView的项目：

Let's try to see what is happening:
The line tries to add an item to something that may be a ListView:

li.SubItems.Add( ... )

添加到视图的内容是：

What is added to the view is:

CType( "..Value to cast..", "..Destination Type..").ToShortDateString()

这里要施放的值是字符串 student_dob，目的地类型是 System.DateTime 。

您要求计算机打开文字字符串student_dob进入DateTime。因此错误。

Here the value to cast is the string "student_dob" and the destination type is System.DateTime.
You are asking the computer to turn the literal string "student_dob" into a DateTime. Thus the error.

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