WPF DataGrid验证/绑定模式错误

Question

我创建了一个非常简单的新项目,仅测试Microsoft WPF DataGrid行为.没有其他涉及,我只使用标准的DataGrid:

<Window x:Class="MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">

    <DataGrid ItemsSource="{Binding Employees, Mode=TwoWay}"
              x:Name="tlv"
              AutoGenerateColumns="False"
              SelectionMode="Extended"
              CanUserAddRows="true"
              SelectionUnit="CellOrRowHeader">
        <DataGrid.Columns>
            <DataGridTextColumn Header="First Name" Binding="{Binding FirstName, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Last Name" Binding="{Binding LastName, Mode=TwoWay}"/>
            <DataGridTextColumn Header="Salary" Binding="{Binding Salary, Mode=TwoWay, ValidatesOnDataErrors=True, UpdateSourceTrigger=LostFocus}"/>
        </DataGrid.Columns>
    </DataGrid>
</Window>

代码背后:

Imports System.Collections.ObjectModel
Imports DataGridTest.Data

Class MainWindow
Sub New()

    ' This call is required by the designer.
    InitializeComponent()

    ' Add any initialization after the InitializeComponent() call.
    Me.DataContext = Me
    Employees = New ObservableCollection(Of Employee)(EmployeeRepository.GetFlatListData())
    BindableSelectedItems = New ObservableCollection(Of Object)
End Sub


Private _employees As ObservableCollection(Of Employee)

Public Property Employees() As ObservableCollection(Of Employee)
    Get
        Return _employees
    End Get
    Set(ByVal value As ObservableCollection(Of Employee))
        _employees = value
    End Set
End Property


Private _bindableSelectedItems As ObservableCollection(Of Object)
Public Property BindableSelectedItems() As ObservableCollection(Of Object)
    Get
        Return _bindableSelectedItems
    End Get
    Set(value As ObservableCollection(Of Object))
        'Set the new value of BindableSelectedItems
        _bindableSelectedItems = value
    End Set
End Property


Private _selectedEmployeeForSelectedItemsSimulation As Employee
Public Property SelectedEmployeeForSelectedItemsSimulation() As Employee
    Get
        Return _selectedEmployeeForSelectedItemsSimulation
    End Get
    Set(value As Employee)
        'Set the new value of SelectedEmployeeForSelectedItemsSimulation
        _selectedEmployeeForSelectedItemsSimulation = value

        If _selectedEmployeeForSelectedItemsSimulation IsNot Nothing AndAlso BindableSelectedItems IsNot Nothing Then
            BindableSelectedItems.Clear()
            BindableSelectedItems.Add(value)
        End If
    End Set
End Property
End Class

Employee类,它实现了IDataErrorInfo:

Imports Microsoft.Practices.Prism.ViewModel
Imports System.Collections.ObjectModel
Imports System.ComponentModel

Namespace Data
Public Class Employee
    Inherits NotificationObject
    Implements IDataErrorInfo

    Public Sub New()

    End Sub

    Public Sub New(ByVal fName As String, ByVal lName As String, ByVal salary As Double)
        FirstName = fName
        LastName = lName
        Me.Salary = salary
    End Sub


    Private _firstName As String
    Public Property FirstName() As String
        Get
            Return _firstName
        End Get
        Set(value As String)
            'Set the new value of FirstName
            _firstName = value

            'Warn any Observers that the FirstName have changed.
            RaisePropertyChanged(Function() Me.FirstName)
        End Set
    End Property


    Private _lastName As String
    Public Property LastName() As String
        Get
            Return _lastName
        End Get
        Set(value As String)
            'Set the new value of LastName
            _lastName = value

            'Warn any Observers that the LastName have changed.
            RaisePropertyChanged(Function() Me.LastName)
        End Set
    End Property


    Private _isSelected As Boolean
    Public Property IsSelected() As Boolean
        Get
            Return _isSelected
        End Get
        Set(value As Boolean)
            'Set the new value of IsSelected
            _isSelected = value

            'Warn any Observers that the IsSelected have changed.
            RaisePropertyChanged(Function() Me.IsSelected)
        End Set
    End Property

    Private _salary As Double
    Public Property Salary() As Double
        Get
            Return _salary
        End Get
        Set(value As Double)
            'Set the new value of Salary
            _salary = value

            'Warn any Observers that the Salary have changed.
            RaisePropertyChanged(Function() Me.Salary)
        End Set
    End Property



    Public ReadOnly Property [Error] As String Implements IDataErrorInfo.Error
        Get
            Return String.Empty
        End Get
    End Property

    Default Public ReadOnly Property Item(columnName As String) As String Implements IDataErrorInfo.Item
        Get

            If Me.Salary <= 0 Then
                Return "The salary must be positive."
            End If

            Return String.Empty
        End Get
    End Property
End Class
End Namespace

到现在为止还挺好.然后,当我在添加新行后尝试更新工资值时会发生以下情况:

该值重置为0!

1. 它为什么这样做？我使用DataGrids的方式出了什么问题？
2. 有解决方法吗？

[编辑] ......和替代方法

我终于发现了看起来像是一种解决方法,即使我仍然不知道我现在认为是Microsoft DataGrid中的错误的原因.

如果在带有验证的datagrid列中指定了绑定模式,则会发生错误 ; 如果相反我没有指定绑定模式,一切都很好.

<DataGridTextColumn Header="Salary" Binding="{Binding Salary, ValidatesOnDataErrors=True, UpdateSourceTrigger=LostFocus}"/>

我不太明白的是,据我所知,默认绑定模式是TwoWay ......好吧,至少我解决了我的问题.

我在这里打开了一个关于Microsoft Connect的错误报告

Answer 1

只是想让你知道，我从微软得到消息，他们说这并不重要，他们甚至不会尝试解决这个错误。

看看这里

因此，这是一个已经存在了一段时间的错误，并且不会很快得到修复。