DatePicker不更新視圖模型，除非焦點更改爲另一個控件

如何使DatePicker控件更新視圖模型而不失焦點？DatePicker不更新視圖模型，除非焦點更改爲另一個控件

我希望能夠運行此示例，鍵入日期12/9/11，單擊窗口關閉按鈕並具有Debug.Assert傳遞。如果我在關閉窗口之前選中文本框，它可以正常工作。

<Window x:Class="DatePickerTest.MainWindow" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     Title="MainWindow" Height="350" Width="525" Closing="MainWindow_OnClosing"> 
    <StackPanel> 
     <DatePicker Name="TheDate" SelectedDate="{Binding Path=SelectedDate}" /> 
     <TextBox/> 
    </StackPanel> 
</Window>

using System; 
using System.ComponentModel; 
using System.Diagnostics; 

namespace DatePickerTest 
{ 
    public partial class MainWindow 
    { 
     public MainWindow() 
     { 
     InitializeComponent(); 
     DataContext = new ViewModel(); 
     } 

     private void MainWindow_OnClosing(object sender, CancelEventArgs e) 
     { 
     var dataContext = DataContext as ViewModel; 
     Debug.Assert(dataContext.SelectedDate == new DateTime(2011, 12, 9)); 
     } 
    } 

    public class ViewModel 
    { 
     public DateTime SelectedDate { get; set; } 
    } 

}

來源

2011-12-09 Robin

嘗試改變UpdateSourceTrigger到PropertyChanged，例如

<DatePicker Name="TheDate" 
      SelectedDate="{Binding Path=SelectedDate 
       , UpdateSourceTrigger=PropertyChanged 
       , Mode=TwoWay}" />

更新

好了，卻彷彿這是一個known issue與DatePicker。您可以綁定到Text屬性來代替，並設置一個TargetNullValue：

<DatePicker 
    Name="TheDate" 
    Text="{Binding Path=SelectedDate 
      , Mode=TwoWay 
      , UpdateSourceTrigger=PropertyChanged 
      , ValidatesOnDataErrors=True 
      , TargetNullValue=''}" 
/>

來源

2011-12-09 21:20:15 devdigital

我更改了示例以使用您的建議，但它不起作用。我認爲UpdateSourceTrigger默認爲PropertyChanged，Mode默認爲TwoWay。 – Robin

我已更新我的答案，並驗證它的工作原理。 – devdigital

**評論來自[Robin]（http://stackoverflow.com/users/108040/）（拒絕編輯）：**這是有效的，謝謝。實際上，在這種情況下所需要的只是：' – Anne

試試這個：

public class CustomDatePicker : DatePicker 
{ 
    protected DatePickerTextBox _datePickerTextBox; 

    public static readonly new DependencyProperty SelectedDateProperty = 
     DependencyProperty.Register(nameof(SelectedDate), typeof(DateTime?), typeof(CustomDatePicker), 
      new FrameworkPropertyMetadata(null, SelectedDateChanged) { BindsTwoWayByDefault = true }); 

    private static new void SelectedDateChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) 
    { 
     ((CustomDatePicker)d).SelectedDate = (DateTime?)e.NewValue; 
    } 

    public new DateTime? SelectedDate 
    { 
     get { return (DateTime?)GetValue(SelectedDateProperty); } 
     set 
     { 
      if (base.SelectedDate != value) base.SelectedDate = value; 
      if (this.SelectedDate != value) SetValue(SelectedDateProperty, value); 
     } 
    } 

    public override void OnApplyTemplate() 
    { 
     base.OnApplyTemplate(); 

     _datePickerTextBox = this.Template.FindName("PART_TextBox", this) as DatePickerTextBox; 
     if (_datePickerTextBox != null) 
      _datePickerTextBox.TextChanged += dptb_TextChanged; 
    } 

    private void dptb_TextChanged(object sender, TextChangedEventArgs e) 
    { 
     int index = _datePickerTextBox.SelectionStart; 
     string text = _datePickerTextBox.Text; 

     DateTime dt; 
     if (DateTime.TryParse(_datePickerTextBox.Text, Thread.CurrentThread.CurrentCulture, 
      System.Globalization.DateTimeStyles.None, out dt)) 
      this.SelectedDate = dt; 
     else 
      this.SelectedDate = null; 

     _datePickerTextBox.Text = text; 
     _datePickerTextBox.SelectionStart = index; 
    } 
}

這是什麼，我發現here的改進版本。它會在用戶輸入時更新SelectedDate。

來源

2017-09-09 07:35:22 Laila

DatePicker不更新視圖模型，除非焦點更改爲另一個控件

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