异常验证与IDataErrorInfo的数据与MVVM实现 [英] Exception validating data with IDataErrorInfo with a MVVM implementation

问题描述

我想验证使用IDataErrorInfo的在我的MVVM应用程序数据，但我遇到了一些问题。

I'm trying to validate data in my MVVM application using IDataErrorInfo, but I'm running into some problems.

当我把我的文本框具有无效值，确认工作正常。但经过我设置文本​​框为有效值的价值，我得到这个异​​常：

When I set my TextBox with an invalid value, the validation works fine. But after I set the value of the TextBox to a valid value and I get this exception:

A first chance exception of type 'System.ArgumentOutOfRangeException' occurred in mscorlib.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll
System.Windows.Data Error: 16 : Cannot get 'Item[]' value (type 'ValidationError') from '(Validation.Errors)' (type 'ReadOnlyObservableCollection`1'). BindingExpression:Path=(0).[0].ErrorContent; DataItem='TextBox' (Name='txtRunAfter'); target element is 'TextBox' (Name='txtRunAfter'); target property is 'ToolTip' (type 'Object') TargetInvocationException:'System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
    at System.ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)
    at System.ThrowHelper.ThrowArgumentOutOfRangeException()
    at System.Collections.Generic.List`1.get_Item(Int32 index)
    at System.Collections.ObjectModel.Collection`1.get_Item(Int32 index)
    at System.Collections.ObjectModel.ReadOnlyCollection`1.get_Item(Int32 index)
    --- End of inner exception stack trace ---
    at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
    at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
    at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
    at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
    at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
    at MS.Internal.Data.PropertyPathWorker.GetValue(Object item, Int32 level)
    at MS.Internal.Data.PropertyPathWorker.RawValue(Int32 k)'

下面是code的观点：

Here is the code for the view:

    <UserControl x:Class="Telbit.TeStudio.View.Controls.TestStepListingStepView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Background="{Binding BackgroundColor}">

    <UserControl.Resources>
        <Style x:Key="TestStepTextBox" TargetType="{x:Type TextBox}">
            <Setter Property="Background" Value="Transparent" />
            <Setter Property="BorderThickness" Value="1"/>
            <Setter Property="BorderBrush" Value="Transparent"/>
            <Setter Property="VerticalContentAlignment" Value="Center"/>
            <Setter Property="HorizontalContentAlignment" Value="Left"/>
            <Setter Property="TextElement.FontSize" Value="10"/>
            <Setter Property="TextElement.FontWeight" Value="Regular"/>
            <Setter Property="Validation.ErrorTemplate" Value="{x:Null}"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type TextBox}">
                        <Border x:Name="Bd" SnapsToDevicePixels="true" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
                            <ScrollViewer x:Name="PART_ContentHost" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsMouseOver" Value="true">
                                <Setter Property="BorderBrush" Value="#3d62a9"/>
                            </Trigger>
                            <Trigger Property="IsFocused" Value="true">
                                <Setter Property="BorderBrush" Value="#3d62a9"/>
                                <Setter Property="Background" Value="White"/>
                            </Trigger>
                            <Trigger Property="Validation.HasError" Value="true">
                                <Setter Property="ToolTip"
                                    Value="{Binding RelativeSource={RelativeSource Self}, 
                                    Path=(Validation.Errors)[0].ErrorContent}"/>
                                <Setter Property="Background" Value="#33FF342D"/>
                                <Setter Property="BorderBrush" Value="#AAFF342D"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </UserControl.Resources>

    ...

    <TextBox Name="txtRunAfter" Grid.Column="4" Text="{Binding RunAfter, ValidatesOnDataErrors=True, NotifyOnValidationError=True, UpdateSourceTrigger=PropertyChanged}" Style="{StaticResource TestStepTextBox}"
         LostFocus="TextBoxLostFocus" PreviewKeyDown="TextBoxPreviewKeyDown" PreviewTextInput="TextBoxPreviewTextInput"/>

    ...

 </UserControl>

这里是code为视图模型：

And here is the Code for the ViewModel:

class TestStepListingStepViewModel : ViewModelBase, IDataErrorInfo
{
    private int _runAfter = 0;
    public int RunAfter
    {
        get
        {
            return _runAfter;
        }

        set
        {
            if (_runAfter != value)
            {
                _runAfter = value;
                OnPropertyChanged("RunAfter");
            }
        }
    }

string IDataErrorInfo.Error
    {
        get { return null; }
    }

    string IDataErrorInfo.this[string columnName]
    {
        get
        {
            string message = null;
            if (columnName == "RunAfter")
                message = validateRunAfter();

            return message;
        }
    }

    private string validateRunAfter()
    {
        if (_runAfter >= _order)
            return "Run After value must be less than its Step Order (#) value.";

        return null;
    }
}

我试图找出什么是错与此两天！有人用一对新鲜的眼光自己看着办吧？

I'm trying to figure out what's wrong with this for two days! Can some one with a pair of fresh eyes figure it out?

编辑：
这里是TextBoxs处理程序的code：

Here is the code of the TextBoxs handlers:

public partial class TestStepListingStepView : UserControl
{
    private string mInvalidCharPattern = "[^0-9]";

    public TestStepListingStepView()
    {
        InitializeComponent();

        DataObject.AddPastingHandler(this.txtRunAfter, new DataObjectPastingEventHandler(TextBoxPasting));
    }

    private void TextBoxLostFocus(object sender, RoutedEventArgs e)
    {
        TextBox txt = sender as TextBox;

        if (txt != null && string.IsNullOrEmpty(txt.Text))
            txt.Text = "0";
    }

    // Catch the space character, since it doesn't trigger PreviewTextInput
    private void TextBoxPreviewKeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Space) { e.Handled = true; }
    }

    // Do most validation here
    private void TextBoxPreviewTextInput(object sender, TextCompositionEventArgs e)
    {
        if (ValidateTextInput(e.Text) == false) { e.Handled = true; }
    }

    // Prevent pasting invalid characters
    private void TextBoxPasting(object sender, DataObjectPastingEventArgs e)
    {
        string lPastingText = e.DataObject.GetData(DataFormats.Text) as string;
        if (ValidateTextInput(lPastingText) == false) { e.CancelCommand(); }
    }

    // Do the validation in a separate function which can be reused
    private bool ValidateTextInput(string aTextInput)
    {
        if (aTextInput == null) { return false; }

        Match lInvalidMatch = Regex.Match(aTextInput, this.mInvalidCharPattern);
        return (lInvalidMatch.Success == false);
    }

}

另外，我使用的.NET Framework 3.5版本。
我的应用程序是非常复杂的，所以我就不能创建一个小的项目，再现只有这一部分。我希望你们中的一些已经有这个问题，知道如何解决它。

Also, I'm using version 3.5 of the .Net Framework. My application is very complex so I won't be able to create a small project that recreates only this part. My hope is that some of you already had this problem and know how to solve it.

再次感谢大家！

推荐答案

没错，马特是正确的。我希望我看了前他的回答时，不要把时间花在寻找问题我自己。

Yep, Matt is right. I wish I looked his answer hour ago, not to spend time finding issue myself.

这是为我工作的另一种选择是使用转换器类来检查，如果错误列表中有项目。所以它看起来像

The other option that worked for me is to use converter class that checks if Errors list has items. So it will look like

<Trigger Property="Validation.HasError" Value="true"> 
<Setter Property="ToolTip" 
   Value="{Binding RelativeSource={RelativeSource Self}, Converter={StaticResource validationConverter},
   Path=(Validation.Errors)}"/> 

public class ValidationConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            ReadOnlyObservableCollection<ValidationError> errors = value as ReadOnlyObservableCollection<ValidationError>;
            if (errors == null) return value;
            if (errors.Count > 0)
            {
                return errors[0].ErrorContent;
            }
            return "";            
        }


        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            throw new NotImplementedException("This method should never be called");
        }

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