當使用INotifyDataErrorInfo進行驗證時，將焦點放回控件

Question

我在silverlight中使用INotifyDataErrorInfo實現進行簡單驗證。

提交時，我驗證所有屬性以顯示所有錯誤。

當驗證發生時，我需要將焦點返回到帶有驗證錯誤的第一個控件。

我們有辦法做到這一點嗎？有什麼建議麼？

Answer 1

比從未更好的遲到:)

我已經實施了此行爲。

首先你需要訂閱你的ViewModel ErrorsChanged和PropertyChanged方法。我在我的構造這樣：

/// <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); 
    } 

然後編寫處理該事件：

/// <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); 
    } 

最後加入方法：

/// <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); 
      } 
     } 
    }