我怎样才能让一个DateTimePicker显示一个空字符串？ [英] How can I make a DateTimePicker display an empty string?

问题描述

我想是能够显示<$​​ C $ C>的DateTimePicker ，有没什么默认值，即没有日期。

I would like to be able to display a DateTimePicker that has a default value of nothing, i.e. no date.

例如，我有一个起始日期 dtTaskStart 和结束日期 dtTaskEnd 的任务，但终日期不知道，并且未填充最初

For example, I have a start date dtTaskStart and an end date dtTaskEnd for a task, but the end date is not known, and not populated initially.

我已经指定了 YYYY-MM-DD 自定义格式为对照组。

I have specified a custom format of yyyy-MM-dd for both controls.

将该值设置为空，或在运行时为空字符串会导致错误，所以我怎么能做到这一点？

Setting the value to null, or an empty string at runtime causes an error, so how can I accomplish this?

我用一个复选框来控制这一领域的实现已经考虑，但仍有显示一个初始值的问题。

I have considered using a checkbox to control the enabling of this field, but there is still the issue of displaying an initial value..

编辑：的
可以说，问题的重复的DateTimePicker空值（.NET），但我找到了解决方案我的问题是不是这个问题的解决方案，所以我觉得应该留在这里为他人找到。

Arguably a duplicate of the question DateTimePicker Null Value (.NET), but the solution I found for my problem is not a solution for that question, so I think it should remain here for others to find..

推荐答案

通过使用 CustomFormat 属性，使用复选框进行模糊值 cbEnableEndDate 作为标志，以指示其他code是否应忽略的值：

Obfuscating the value by using the CustomFormat property, using checkbox cbEnableEndDate as the flag to indicate whether other code should ignore the value:

    If dateTaskEnd > Date.FromOADate(0) Then
        dtTaskEnd.Format = DateTimePickerFormat.Custom
        dtTaskEnd.CustomFormat = "yyyy-MM-dd"
        dtTaskEnd.Value = dateTaskEnd 
        dtTaskEnd.Enabled = True
        cbEnableEndDate.Checked = True
    Else
        dtTaskEnd.Format = DateTimePickerFormat.Custom
        dtTaskEnd.CustomFormat = " "
        dtTaskEnd.Value = Date.FromOADate(0)
        dtTaskEnd.Enabled = False
        cbEnableEndDate.Checked = False
    End If

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