Question

我正在开发一个带有两个DateTimePicker控件的WinForms UI。最初，我想将控件的值设置为null，直到用户选择日期。如果用户未选择日期，则会将值传递给数据库。

默认采用当前日期。

你能不能提出建议或附上一段能帮助我的代码。

我已尝试设置MinDate属性但不起作用。

代码位于C＃.Net。

谢谢，马纳里。

Answer 1

我认为最好的解决方案是使用内置复选框，告诉用户是否指定了值。

设置控件属性ShowCheckBox = true

将值绑定到它时，请执行类似

的操作

 if (value == DateTime.MinValue) {
    datePicker.Checked = false;
  } else {
    datePicker.Checked = true;
    datePicker.Value = value;
  }

回读值时，请检查Checked属性。

如果您在取消选中时不喜欢显示的值，则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.
  }

Answer 2

我知道这是一篇较旧的帖子，但其他人可能仍然觉得这很有用。它相当优雅和简洁。我在.Net 4.0 DateTimePicker中使用它，但早期版本应该使用最小的调整。它利用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;

Answer 3

要在DateTimePicker控件中显示空值，请在Designer.cs文件中进行以下更改：

this.DateTimePicker.Format = System.Windows.Forms.DateTimePickerFormat.Custom;
this.DateTimePicker.CustomFormat = " ";

当用户选择日期时，编码控件的ValueChanged属性并根据您的需要制作格式。这将在控件中显示日期。

以上只显示UI中的控件为空白，但默认值仍为当前日期。

如果要将值设置/初始化为null或空字符串：

声明临时字符串变量say temp
temp = DateTimePicker.CustomFormat.ToString();
检查temp是否为空字符串。如果是这样，你可以随意处理。

这是我找到的最简单的解决方法。

Answer 4

假设dtpStartDate是你的DateTimePicker控件。

在Page_Load -

中编写此代码

`dtpStartDate.Format = DateTimePickerFormat.Custom;
            dtpStartDate.CustomFormat = " ";`

将此代码写入Value_Changed事件 -

`startDate = Convert.ToString(dtpStartDate.Value);
        dtpStartDate.Format = DateTimePickerFormat.Short;`

这里选择'short'作为格式。您可以选择“长”和其他可用选项。

Answer 5

可能需要使用TextBox的Appereance创建UserControl，当用户单击Calender Show时，当您选择Date时将其设置为TextBox。它将允许空值。

DateTimePicker不允许null。

Answer 6

我希望这可以帮助您Link1 在选择器字段中显示空白

这也是Link2

Answer 7

这是我使用的可以为空的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

Answer 8

dateTimePicker1.CustomFormat = " ";

将DateTimePicker值设置为null

8 个答案: