在Silverlight中，如何找到绑定到有错误的模型的第一个字段，以便可以将其聚焦？

问题描述

| 问候 我有一个绑定到实现INotifyDataErrorInfo的模型对象的Silverlight表单，并在单击“保存”按钮时进行了验证。如果模型上的某些属性返回无效，Silverlight将自动突出显示绑定的输入字段。 有没有办法将焦点设置到第一个无效字段？ 更新： 甚至有办法查看输入字段是否处于该无效显示状态吗？如果可以检测到，可以遍历各个字段并手动设置焦点。 谢谢， 马修     

解决方法

        我已经实现了这种行为。 首先，您需要订阅ViewModel

ErrorsChanged

和

PropertyChanged

方法。我在我的构造函数中这样做：

    /// <summary>
    /// Initializes new instance of the View class.
    /// </summary>
    public View(ViewModel viewModel)
    {
        if (viewModel == null)
            throw new ArgumentNullException(\"viewModel\");

        // Initialize the control
        InitializeComponent();  // exception

        // Set view model to data context.
        DataContext = viewModel;

        viewModel.PropertyChanged += new PropertyChangedEventHandler(_ViewModelPropertyChanged);
        viewModel.ErrorsChanged += new EventHandler<DataErrorsChangedEventArgs>(_ViewModelErrorsChanged);
    }

然后为该事件编写处理程序：

    /// <summary>
    /// If model errors has changed and model still have errors set flag to true,/// if we dont have errors - set flag to false.
    /// </summary>
    /// <param name=\"sender\">Ignored.</param>
    /// <param name=\"e\">Ignored.</param>
    private void _ViewModelErrorsChanged(object sender,DataErrorsChangedEventArgs e)
    {
        if ((this.DataContext as INotifyDataErrorInfo).HasErrors)
            _hasErrorsRecentlyChanged = true;
        else
            _hasErrorsRecentlyChanged = false;
    }

    /// <summary>
    /// Iterate over view model visual childrens.
    /// </summary>
    /// <param name=\"sender\">Ignored.</param>
    /// <param name=\"e\">Ignored.</param>
    private void _ViewModelPropertyChanged(object sender,PropertyChangedEventArgs e)
    {
        if ((this.DataContext as INotifyDataErrorInfo).HasErrors)
            _LoopThroughControls(this);
    }

最后添加方法：

    /// <summary>
    /// If we have error and we haven\'t already set focus - set focus to first control with error.
    /// </summary>
    /// <remarks>Recursive.</remarks>
    /// <param name=\"parent\">Parent element.</param>
    private void _LoopThroughControls(UIElement parent)
    {
        // Check that we have error and we haven\'t already set focus
        if (!_hasErrorsRecentlyChanged)
            return;

        int count = VisualTreeHelper.GetChildrenCount(parent);

        // VisualTreeHelper.GetChildrenCount for TabControl will always return 0,so we need to 
        // do this branch of code.
        if (parent.GetType().Equals(typeof(TabControl)))
        {
            TabControl tabContainer = ((TabControl)parent);
            foreach (TabItem tabItem in tabContainer.Items)
            {
                if (tabItem.Content == null)
                    continue;

                _LoopThroughControls(tabItem.Content as UIElement);
            }
        }

        // If element has childs.
        if (count > 0)
        {
            for (int i = 0; i < count; i++)
            {
                UIElement child = (UIElement)VisualTreeHelper.GetChild(parent,i);

                if (child is System.Windows.Controls.Control)
                {
                    var control = (System.Windows.Controls.Control)child;

                    // If control have error - we found first control,set focus to it and 
                    // set flag to false.
                    if ((bool)control.GetValue(Validation.HasErrorProperty))
                    {
                        _hasErrorsRecentlyChanged = false;
                        control.Focus();
                        return;
                    }
                }

                _LoopThroughControls(child);
            }
        }
    }

    ,        您可以在视图中使用ValidationSummary来显示模型引发的所有验证错误。当您单击ValidationSummary中的错误时，引起验证错误的控件将集中显示。 在Silverlight工具包的示例中可以找到ValidationSummary的示例。 直到现在，我还没有在任何应用程序中使用ValidationSummary，因此我无法为您提供有关用法或“如何使用”的任何信息，但这也许会对您有所帮助