Setting focus to UI control in WPF MVVM Way on Validation.HasError

Question

Problem: Validation.HasError automatically highlights the control that has Error via INotifyDataErrorInfo implementation.

My problem is i need to set focus on that specific control when it has ERror.

How do I do That?

Jacobine

Answer 1

I have gone through several articles in Stackoverflow and other sites and i finally wish to address this problem.

   <Style TargetType="TextBox" >
                        <Setter Property="OverridesDefaultStyle" Value="false"/>
                        <Setter Property="VerticalAlignment" Value="Center"/>
                        <Setter Property="HorizontalAlignment" Value="Left"/>
                        <Setter Property="Margin" Value="5,3" />
                        <Style.Triggers>
                            <Trigger Property="Validation.HasError" Value="True">
                                <Setter Property="FocusManager.FocusedElement" Value="{Binding RelativeSource={RelativeSource Self}}"/>
                            </Trigger>
                        </Style.Triggers>
                    </Style>

Setting FocusedElement did the trick. :) This can also be used to set focus using a boolean property in ViewModel via DataTrigger than a simple trigger.

Jacobine

Answer 2

Wpf MVVM Used FocusExtension Behaviors

 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();

        }


    }
}

Xaml Code

            <TextBox
                    behavior:FocusExtension.IsFocused="{Binding NameFocus}"
                    Text="{Binding Customer_Name,Mode=TwoWay, UpdateSourceTrigger=PropertyChanged }"
                    x:Name="txtname" 
                    CharacterCasing="Upper"
                    Grid.Column="3"
                    Grid.Row="1"
                    TextWrapping="Wrap" 
                    BorderThickness="1,1,1,0.5"
                    >

            </TextBox>

MVVM Propery in View Model

 public const string NameFocusPropertyName = "NameFocus";
    private bool _NameFocus = default(bool);
    public bool NameFocus
    {
        get
        {
            return _NameFocus;
        }

        set
        {
            if (_NameFocus == value)
            {
                return;
            }

            _NameFocus = value;
            RaisePropertyChanged(NameFocusPropertyName);
        }
    }

Set Load Event

NameFocus=true

Adjunct