将焦点设置文本框在WPF从视图模型（C＃） [英] Set focus on textbox in WPF from view model (C#)

问题描述

我有一个文本框和按钮在我看来。

现在我检查后，按一下按钮一个条件，如果条件证明是假的，显示消息给用户，然后我必须设置光标到文本框控件。

Now I am checking a condition upon button click and if the condition turns out to be false, displaying the message to the user, and then I have to set the cursor to the text box control.

if (companyref == null)
{
Lipper.Nelson.AdminClient.Main.Views.ContactPanels.CompanyAssociation cs = new Lipper.Nelson.AdminClient.Main.Views.ContactPanels.CompanyAssociation(); 

MessageBox.Show("Company does not exist.", "Error", MessageBoxButton.OK,
                    MessageBoxImage.Exclamation);

    cs.txtCompanyID.Focusable = true;

    System.Windows.Input.Keyboard.Focus(cs.txtCompanyID);

}

以上code是在视图模型。

The above code is in the view model.

该CompanyAssociation认为名字。

The CompanyAssociation is the view name.

但光标未在文本框设置越来越。

在XAML是因为在

<igEditors:XamTextEditor KeyDown="xamTextEditorAllowOnlyNumeric_KeyDown" 
  Name="txtCompanyID" ValueChanged="txtCompanyID_ValueChanged"  Text="{Binding 
  Company.CompanyId, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="{Binding 
  ActualWidth, ElementName=border}" Grid.Column="1" Grid.Row="0" 
  VerticalAlignment="Top" Margin="0,5,0,0" HorizontalAlignment="Stretch"
  IsEnabled="{Binding Path=IsEditable}" />

<Button Template="{StaticResource buttonTemp1}" Command="{Binding ContactCommand}" 
  CommandParameter="searchCompany" Content="Search"  Width="80"  Grid.Column="2" 
  Grid.Row="0" VerticalAlignment="Top" Margin="0" HorizontalAlignment="Left"  
  IsEnabled="{Binding Path=IsEditable}" />

请帮忙

推荐答案

让我来回答你的问题三个部分。

Let me answer to your question in three parts.

1. 我不知道什么是cs.txtCompanyID在你的榜样？它是一个TextBox控件？如果是，那么你是在一个错误的方式。一般来讲这不是一个好主意，有任何引用您的视图模型来UI。你可以问为什么？不过这是另外一个问题后＃2。）

1. I'm wondering what is "cs.txtCompanyID" in your example? Is it a TextBox control? If yes, then you are on a wrong way. Generally speaking it's not a good idea to have any reference to UI in your ViewModel. You can ask "Why?" but this is another question to post on Stackoverflow :).

跟踪与焦点问题的最好办法是...调试.NET源$ C ​​$ C。别开玩笑了。它救了我很多时间很多次。为了让.NET源$ C ​​$ C调试参考<一个href=\"http://blogs.msdn.com/sburke/archive/2008/01/16/configuring-visual-studio-to-debug-net-framework-source-$c$c.aspx\">Shawn Bruke的博客。

The best way to track down issues with Focus is... debugging .Net source code. No kidding. It saved me a lot of time many times. To enable .net source code debugging refer to Shawn Bruke's blog.

最后，我用它来设置焦点从视图模型的普遍做法是附加属性。我写了很简单的附加属性，它可以在任何的UIElement设置。它可以被绑定到视图模型的财产IsFocused为例。在这里，它是：

Finally, general approach that I use to set focus from ViewModel is Attached Properties. I wrote very simple attached property, which can be set on any UIElement. And it can be bound to ViewModel's property "IsFocused" for example. Here it is:

public static class FocusExtension
{
    public static bool GetIsFocused(DependencyObject obj)
    {
        return (bool) obj.GetValue(IsFocusedProperty);
    }

    public static void SetIsFocused(DependencyObject obj, bool value)
    {
        obj.SetValue(IsFocusedProperty, value);
    }

    public static readonly DependencyProperty IsFocusedProperty =
        DependencyProperty.RegisterAttached(
            "IsFocused", typeof (bool), typeof (FocusExtension),
            new UIPropertyMetadata(false, OnIsFocusedPropertyChanged));

    private static void OnIsFocusedPropertyChanged(
        DependencyObject d, 
        DependencyPropertyChangedEventArgs e)
    {
        var uie = (UIElement) d;
        if ((bool) e.NewValue)
        {
            uie.Focus(); // Don't care about false values.
        }
    }
}

现在在你的视图（XAML）可以将此属性绑定到您的视图模型：

Now in your View (in XAML) you can bind this property to your ViewModel:

<TextBox local:FocusExtension.IsFocused="{Binding IsUserNameFocused}" />

希望这有助于:)。如果它不参考答案＃2。

Hope this helps :). If it doesn't refer to the answer #2.

干杯。

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