Question

我在WPF 4.5项目中做了一个简单的INotifyDataErrorInfo实现。这是WPF的新界面，但已在Silverlight中使用了一段时间。

我知道NET4.5仍然被认为是alpha版，但我正在尝试解决它是否是我的代码或错误的框架。

接口按预期工作，但在将对象绑定到DataGrid时失败。

我收到的例外是：

System.NullReferenceException未被用户代码
处理 Message =对象引用未设置为对象的实例 Source = PresentationFramework StackTrace：在MS.Internal.Data.ClrBindingWorker.OnDataErrorsChanged（INotifyDataErrorInfo） indei，String propName）在MS.Internal.Data.PropertyPathWorker.OnErrorsChanged（Object sender，DataErrorsChangedEventArgs e）在System.Windows.WeakEventManager.ListenerList`1.DeliverEvent（Object sender，EventArgs e，Type managerType）在System.Windows.WeakEventManager.DeliverEvent（Object sender，EventArgs args）在System.ComponentModel.ErrorsChangedEventManager.OnErrorsChanged（Object sender，DataErrorsChangedEventArgs args）在INotifyDataErrorInfoTest中的INotifyDataErrorInfoTest.Person.NotifyErrorsChanged（String属性）：第109行在INotifyDataErrorInfoTest中的INotifyDataErrorInfoTest.Person.AddErrorForProperty（字符串属性，字符串错误）：第122行在INotifyDataErrorInfoTest中的INotifyDataErrorInfoTest.Person.Validate（String propertyName）：Person.cs：第150行 at INotifyDataErrorInfoTest.Person.set_FirstName（String value）INotifyDataErrorInfoTest \ Person.cs：第18行

代码位于http://dl.dropbox.com/u/14740106/INotifyDataErrorInfoTest.zip

下方或项目中

如果一致认为这是一个错误，那么我将发布到MS Connect。

测试：有两个文本框绑定到Person对象的单个实例。将第一个文本框设置为具有值的James，它将无法通过验证并显示红色框。如果将网格中任何用户的名字设置为James，则会抛出异常。

PS：我知道它不是MVVM，但它只是为了证明或反驳这个问题。

 public class Person : INotifyDataErrorInfo, INotifyPropertyChanged
    {
        string _firstName;
        public string FirstName
        {
            get { return _firstName; }
            set
            {
                _firstName = value;
                Validate("FirstName");
                OnPropertyChanged("FirstName");
            }
        }

        string _lastName;
        public string LastName
        {
            get { return _lastName; }
            set
            {
                _lastName = value;
                Validate("LastName");
                OnPropertyChanged("LastName");
            }
        }

        public Person()
        {
        }

        public Person(string first, string last)
        {
            this._firstName = first;
            this._lastName = last;
        }

        #region INotifyPropertyChanged Members

        /// <summary>
        /// Event to indicate that a property has changed.
        /// </summary>
        [field: NonSerialized]
        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary>
        /// Called when a property is changed
        /// </summary>
        /// <param name="propertyName">The name of the property that has changed.</param>
        protected virtual void OnPropertyChanged(string propertyName)
        {
            OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
        }

        /// <summary>
        /// Called when a property is changed
        /// </summary>
        /// <param name="e">PropertyChangedEventArgs</param>
        protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
        {

            //Validate the property
            Validate(e.PropertyName);

            if (null != PropertyChanged)
            {
                PropertyChanged(this, e);
            }

        }

        #endregion

        #region INotifyDataErrorInfo Members

        public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
        private Dictionary<string, List<string>> _errors = new Dictionary<string, List<string>>();

        public IEnumerable GetErrors(string propertyName)
        {
            if (string.IsNullOrEmpty(propertyName))
            {
                return (_errors.Values);
            }

            MakeOrCreatePropertyErrorList(propertyName);
            return _errors[propertyName];
        }

        public bool HasErrors
        {
            get
            {
                return (_errors.Where(c => c.Value.Count > 0).Count() > 0);
            }
        }

        void NotifyErrorsChanged(string property)
        {
            if (ErrorsChanged != null)
            {
                ErrorsChanged(this, new DataErrorsChangedEventArgs(property));
            }
        }
        public void ClearErrorFromProperty(string property)
        {
            MakeOrCreatePropertyErrorList(property);
            _errors[property].Clear();
            NotifyErrorsChanged(property);
        }
        public void AddErrorForProperty(string property, string error)
        {
            MakeOrCreatePropertyErrorList(property);
            _errors[property].Add(error);
            NotifyErrorsChanged(property);
        }

        void MakeOrCreatePropertyErrorList(string propertyName)
        {
            if (!_errors.ContainsKey(propertyName))
            {
                _errors[propertyName] = new List<string>();
            }
        }

        #endregion

        /// <summary>
        /// Force the object to validate itself using the assigned business rules.
        /// </summary>
        /// <param name="propertyName">Name of the property to validate.</param>
        public void Validate(string propertyName)
        {
            if (string.IsNullOrEmpty(propertyName))
            {
                return;
            }

            if (propertyName == "FirstName")
            {
                if (FirstName == "James")
                {
                    AddErrorForProperty(propertyName, "FirstName can't be James");
                }
                else
                {
                    ClearErrorFromProperty(propertyName);
                }
            }
        }
    }

public class NameList : ObservableCollection<Person>
    {
        public NameList()
            : base()
        {
            Add(new Person("Willa", "Cather"));
            Add(new Person("Isak", "Dinesen"));
            Add(new Person("Victor", "Hugo"));
            Add(new Person("Jules", "Verne"));
        }
    }

   public partial class MainWindow : Window
    {

        Person _person = new Person();

        public MainWindow()
        {
            InitializeComponent();
            DataContext = this;
        }

        public Person Person
        {
            get { return _person; }
        }
}

<Window x:Class="INotifyDataErrorInfoTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:c="clr-namespace:INotifyDataErrorInfoTest"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <c:NameList x:Key="NameListData"/>
    </Window.Resources>
    <StackPanel>
        <StackPanel.Resources>
            <Style TargetType="TextBox">
                <Setter Property="Margin" Value="5"></Setter>
            </Style>
        </StackPanel.Resources>
        <TextBox Text="{Binding Person.FirstName, Mode=TwoWay, ValidatesOnNotifyDataErrors=True}"/>
        <TextBox Text="{Binding Person.LastName, Mode=TwoWay, ValidatesOnNotifyDataErrors=True}"/>
        <TextBlock>To generate an error, set the FirstName of any row to James.
        </TextBlock>
        <DataGrid ItemsSource="{Binding Source={StaticResource NameListData}}" AutoGenerateColumns="True"></DataGrid>
    </StackPanel>
</Window>

Answer 1

答案是肯定的。我打开了一个ticket with Microsoft，他们已经确认代码很好，这是.NET 4.5 DataGrid的一个错误。

这是我们的错误，不是你的。编辑DataGrid单元格时，DataGrid会丢弃“显示”模板的绑定，并将其替换为“编辑”模板的绑定。丢弃的绑定应该停止监听INDEI.ErrorsChanged事件。他们没有（这是错误），但他们不准备再参加活动了。当事件到达时，会发生空引用崩溃。

这将在最终版本中修复。感谢您查找并报告。

非常大的bug必须等到最终版本。我们希望它能在下一个版本中得到解决。

是否为WPF 4.5 DataGrids打破了INotifyDataErrorInfo

1 个答案: