Question

我有一个视窗申请表,对进入日期进行海关控制。这从文本箱中继承,对基本商业目标具有约束性,并落实价值财产。

一切都行之有效,除非控制证明它更新了受约束的财产,即使它有变。这是一个问题,因为Im利用实体框架和实体变更财产造成数据库的相应领域,每当用户开放并关闭这种控制的形式时,都要更新。

该守则是:

Public Class TextBoxDate
Inherits TextBox

Public ValueChanged As EventHandler

Private _dateValue As Nullable(Of Date) = Nothing
<Bindable(True)> _
<Category("Appearance")> _
Public Property Value() As Nullable(Of Date)
      Bind to the Value property instead of the Text property, as the latter will not allow
      the user to delete the contents of the textbox. The Value property provides support for nulls.
    Get
        Value = _dateValue
    End Get
    Set(ByVal value As Nullable(Of Date))
        _dateValue = value
          Update the text in the textbox
        If value.HasValue Then
            Text = CDate(value).ToShortDateString
        Else
            Text = vbNullString
        End If
        OnValueChanged()
    End Set
End Property

Private Sub OnValueChanged()
    If (ValueChanged IsNot Nothing) Then
        ValueChanged(Me, New EventArgs())
    End If

End Sub

Private Sub TextBoxDate_Enter(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Enter

    _userEntered = True

End Sub

Private Sub TextBoxDate_Leave(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Leave

    _userEntered = False

End Sub

Protected Overrides Sub OnValidating(ByVal e As System.ComponentModel.CancelEventArgs)

    If _userEntered Then
        If Me.TextLength = 0 Then
              Null value will be saved to the database via the bound Value property
            If Value IsNot Nothing Then
                Value = Nothing
            End If
        Else
            Dim dateValue As Date
            If Date.TryParseExact(Text, "d/M/yyyy", System.Globalization.DateTimeFormatInfo.InvariantInfo, Globalization.DateTimeStyles.None, dateValue) Then
                If Value Is Nothing Or (dateValue <> Value) Then
                    Value = CDate(Text)
                End If
            Else
                e.Cancel = True
            End If
        End If
    End If

    MyBase.OnValidating(e)

End Sub

End Class

这使我mad。任何帮助都会受到高度赞赏。

Scott

Answer 1

当你确定文本箱的约束性时,你可具体说明

Binding custNameBinding = new Binding("Text", ds, "customers.custName");
custNameBinding.DataSourceUpdateMode = DataSourceUpdateMode.OnPropertyChanged;
custNameTextBox.DataBindings.Add(custNameBinding);

MSDN文件说,“每当控制财产的价值发生变化时,数据来源就会更新”。

友情链接