我正在开发一个带有两个 DateTimePicker
控件的 WinForms UI。最初,我希望将控件的值设置为 null,直到用户选择日期。如果用户没有选择日期,它将向数据库传递空值。
默认情况下,它采用当前日期。
请您建议或附加代码片段,以帮助我解决问题。
我已经尝试设置 MinDate
属性,但它并不起作用。
该代码使用 C# .Net 编写。
谢谢,Manali。
我正在开发一个带有两个 DateTimePicker
控件的 WinForms UI。最初,我希望将控件的值设置为 null,直到用户选择日期。如果用户没有选择日期,它将向数据库传递空值。
默认情况下,它采用当前日期。
请您建议或附加代码片段,以帮助我解决问题。
我已经尝试设置 MinDate
属性,但它并不起作用。
该代码使用 C# .Net 编写。
谢谢,Manali。
ShowCheckBox = true
当将值绑定到它时,执行以下操作: if (value == DateTime.MinValue) {
datePicker.Checked = false;
} else {
datePicker.Checked = true;
datePicker.Value = value;
}
读取值时,请检查Checked
属性。
如果您不喜欢未选中时显示的值,可以将其与其他建议结合使用。
if (!datePicker.Checked) {
// hide date value since it's not set
datePicker.CustomFormat = " ";
datePicker.Format = DateTimePickerFormat.Custom;
} else {
datePicker.CustomFormat = null;
datePicker.Format = DateTimePickerFormat.Long; // set the date format you want.
}
我知道这篇文章已经有点老了,但其他人可能仍然会发现它有用。它相当优美而简洁。我使用它与 .Net 4.0 DateTimePicker 一起使用,但早期版本只需要进行少量调整即可。它利用了 MinDate 和 Checked。
// Use ValueChanged to decide if the value should be displayed:
dateTimePicker1.ValueChanged += (s, e) => { dateTimePicker1.CustomFormat = (dateTimePicker1.Checked && dateTimePicker1.Value != dateTimePicker1.MinDate) ? "MM/dd/yyyy" : " "; };
//When getting the value back out, use something like the following:
DateTime? dt = (dateTimePicker1.Checked && dateTimePicker1.Value != dateTimePicker1.MinDate) ? (DateTime?) dateTimePicker1.Value : null;
// or
DateTime dt2 = (dateTimePicker1.Checked && dateTimePicker1.Value != dateTimePicker1.MinDate) ? dateTimePicker1.Value : DateTime.MinValue;
DateTimePicker
控件中显示 null 值,请在 Designer.cs
文件中进行以下更改:this.DateTimePicker.Format = System.Windows.Forms.DateTimePickerFormat.Custom;
this.DateTimePicker.CustomFormat = " ";
dtpStartDate
是您的DateTimePicker控件。`dtpStartDate.Format = DateTimePickerFormat.Custom;
dtpStartDate.CustomFormat = " ";`
`startDate = Convert.ToString(dtpStartDate.Value);
dtpStartDate.Format = DateTimePickerFormat.Short;`
在这里选择“短”作为格式,你可以选择“长”和其他可用选项。
也许您需要创建一个外观类似于文本框的UserControl,当用户单击日历时显示,选择日期后将其设置为文本框。它将允许空值。
DateTimePicker不允许为空。
DateTime
的Nullable
属性,第二个链接将帮助您通过CodeProject示例实现相同的效果,该示例重写了Value
属性以接受DateTime?
。这是实现您想要的唯一方法。 - V4Vendetta这是我使用的可空日期时间选择器的代码:
Public Class DateTimePickerNullable
Inherits DateTimePicker
Public Shadows Event GotFocus(sender As Object, e As EventArgs)
Public Shadows Event LostFocus(sender As Object, e As EventArgs)
Private fvalue As DateTime?
Private NoValueChange As Boolean = False
Public Shadows Property Value As DateTime?
Get
Return fvalue
End Get
Set(value As DateTime?)
fvalue = value
If fvalue Is Nothing Then
Me.Format = DateTimePickerFormat.Custom
Me.CustomFormat = Space(Now.ToShortDateString.Length)
NoValueChange = True
MyBase.Value = Now
NoValueChange = False
Else
Me.Format = DateTimePickerFormat.Short
NoValueChange = True
MyBase.Value = value.Value
NoValueChange = False
End If
End Set
End Property
Protected Overrides Sub OnValueChanged(eventargs As EventArgs)
If Not NoValueChange Then
Value = MyBase.Value
End If
MyBase.OnValueChanged(eventargs)
End Sub
Protected Overrides Sub OnKeyDown(e As KeyEventArgs)
If e.KeyCode = Keys.Delete Then
Value = Nothing
End If
If Me.Format = DateTimePickerFormat.Custom Then
Try
If Char.IsNumber(ChrW(e.KeyCode)) Then
If Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat.ShortDatePattern.ToLower.StartsWith("m") Then
Value = New Date(Now.Year, CInt(ChrW(e.KeyCode).ToString), Now.Day)
Else
Value = New Date(Now.Year, Now.Month, CInt(ChrW(e.KeyCode).ToString))
End If
SendKeys.Send(ChrW(e.KeyCode))
Exit Sub
End If
Catch
End Try
End If
MyBase.OnKeyDown(e)
End Sub
Private HasFocus As Boolean = False
Protected Overrides Sub OnGotFocus(e As EventArgs)
MyBase.OnGotFocus(e)
If Not HasFocus Then
HasFocus = True
RaiseEvent GotFocus(Me, New EventArgs)
End If
End Sub
Protected Overrides Sub OnValidated(e As EventArgs)
MyBase.OnValidated(e)
HasFocus = False
RaiseEvent LostFocus(Me, New EventArgs)
End Sub
End Class
dateTimePicker1.CustomFormat = " ";