在UserControl中显示验证错误

Question

我不确定为什么验证状态不会反映在我的用户控件中.我抛出异常但由于某种原因控件没有显示验证状态...当我Textbox在我的MainPage上使用标准(现在在我的例子中注释掉)时它显示错误状态,不确定为什么它不是当它包裹.

我已经减少了这一点,所以基本上它是一个包装的用户控件TextBox.我错过了什么？

MyUserControl XAML:

<UserControl x:Class="ValidationWithUserControl.MyUserControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">

    <Grid x:Name="LayoutRoot" Background="White">
        <TextBox x:Name="TextBox"/>
    </Grid>
</UserControl>

MyUserControl代码背后:

public partial class MyUserControl : UserControl
{
    public MyUserControl()
    {
        InitializeComponent();

        this.Loaded += new RoutedEventHandler(MyUserControl_Loaded);
        this.TextBox.Unloaded += new RoutedEventHandler(TextBox_Unloaded);
    }

    public string Value
    {
        get { return (string)base.GetValue(ValueProperty); }
        set { base.SetValue(ValueProperty, value); }
    }

    public static DependencyProperty ValueProperty =
        DependencyProperty.Register(
        "Value",
        typeof(string),
        typeof(MyUserControl),
        new PropertyMetadata(null));

    private void MyUserControl_Loaded(object sender, RoutedEventArgs e)
    {
        this.TextBox.SetBinding(TextBox.TextProperty, new Binding()
        {
            Source = this,
            Path = new PropertyPath("Value"),
            Mode = BindingMode.TwoWay,
            ValidatesOnExceptions = true,
            NotifyOnValidationError= true
        });  
    }

    private void TextBox_Unloaded(object sender, RoutedEventArgs e)
    {
        this.TextBox.ClearValue(TextBox.TextProperty);
    }
}

我的主页XAML:

<Grid x:Name="LayoutRoot" Background="LightBlue">
    <StackPanel>
        <uc:MyUserControl x:Name="UC" Value="{Binding Path=Value, Mode=TwoWay}" Height="20" Width="100" />
        <!--TextBox x:Name="MS" Text="{Binding Path=Value, Mode=TwoWay, ValidatesOnExceptions=True, NotifyOnValidationError=True}" Height="20" Width="100" /-->
    </StackPanel>
</Grid>

我的MainPage代码背后:

public partial class MainPage : UserControl
{
    private Model model;
    //private Model model2;

    public MainPage()
    {
        InitializeComponent();
        this.model = new Model("UC");
        //this.model2 = new Model("MS");
        this.UC.DataContext = this.model;
        //this.MS.DataContext = this.model2;
    }
}

我的型号:

public class Model
{
    public Model(string answer)
    {
        this.answer = answer;
    }

    private string answer;
    public string Value
    {
        get
        {
            return this.answer;
        }
        set
        {
            if (!String.IsNullOrEmpty(value))
                this.answer = value;
            else
                throw new Exception("Error");
        }
    }
}

Answer 1

好吧,我终于想出了如何处理这个问题.

您需要做的是从原始绑定复制验证并将其发送到Textbox绑定.

要实现这一点,您需要做的第一件事是在用户控件中实现INotifyDataErrorInfo接口.然后,您必须验证用户控件以获取GetErrors函数的确切验证文本(可以使用Validation.GetErrors完成此操作).

这是一个基本的实现,它在VB中,但我相信你明白了.

    Public Event ErrorsChanged(ByVal sender As Object, ByVal e As System.ComponentModel.DataErrorsChangedEventArgs) Implements System.ComponentModel.INotifyDataErrorInfo.ErrorsChanged

Public Function GetErrors(ByVal propertyName As String) As System.Collections.IEnumerable Implements System.ComponentModel.INotifyDataErrorInfo.GetErrors
    Dim returnValue As System.Collections.IEnumerable = Nothing

    Dim errorMessage As String = Nothing


    If propertyName = "Value" Then

        If Validation.GetErrors(Me).Count = 0 Then
            errorMessage = ""
        Else
            errorMessage = Validation.GetErrors(Me).First.ErrorContent.ToString
        End If

        If String.IsNullOrEmpty(errorMessage) Then
            returnValue = Nothing
        Else
            returnValue = New List(Of String)() From {errorMessage}
        End If

    End If

    Return returnValue

End Function

Public ReadOnly Property HasErrors As Boolean Implements System.ComponentModel.INotifyDataErrorInfo.HasErrors
    Get
        Return Validation.GetErrors(Me).Any()
    End Get
End Property

接下来要做的就是通知你控制它变得无效.您必须在2个地方执行此操作.

第一个将在BindingValidationError事件上.第二个将在Value PropertyChangedCallback函数中(必须在注册DependencyProperty时指定)

Public Shared ValueProperty As DependencyProperty = DependencyProperty.Register("Value", GetType(String), GetType(XDateTimePicker), New PropertyMetadata(Nothing, AddressOf ValuePropertyChangedCallback))

Public Shared Sub ValuePropertyChangedCallback(ByVal dependencyObject As DependencyObject, ByVal dependencyPropertyChangedEventArgs As DependencyPropertyChangedEventArgs)
    DirectCast(dependencyObject, MyUserControl).NotifyErrorsChanged("Value")
End Sub

Private Sub MyUserControl_BindingValidationError(ByVal sender As Object, ByVal e As System.Windows.Controls.ValidationErrorEventArgs) Handles Me.BindingValidationError
    Me.NotifyErrorsChanged("Value")
End Sub

Public Sub NotifyErrorsChanged(ByVal propertyName As String)
    RaiseEvent ErrorsChanged(Me, New System.ComponentModel.DataErrorsChangedEventArgs(propertyName))
End Sub

大部分工作现在已完成,但您仍需要对绑定进行一些调整.

创建TextBox绑定时,需要将NotifyOnValidationError设置为False以避免原始绑定和Textbox绑定之间的通知循环. 需要将ValidatesOnExceptions,ValidatesOnDataErrors和ValidatesOnNotifyDataErrors设置为True.

        Dim binding As New System.Windows.Data.Binding

    binding.Source = Me
    binding.Path = New System.Windows.PropertyPath("Value")
    binding.Mode = Data.BindingMode.TwoWay
    binding.NotifyOnValidationError = False 
    binding.ValidatesOnExceptions = True
    binding.ValidatesOnDataErrors = True
    binding.ValidatesOnNotifyDataErrors = True

    Me.TextBox1.SetBinding(TextBox.TextProperty, binding)

最后,您需要在XAML 中将NotifyOnValidationError和ValidatesOnNotifyDataErrors属性设置为True.

<uc:MyUserControl x:Name="UC" Value="{Binding Path=Value, Mode=TwoWay, NotifyOnValidationError=True, ValidatesOnNotifyDataErrors=True}" Height="20" Width="100" />