How to do Event Handling of text boxes using MVVM

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C#

private void txtUsername_LostFocus(object sender, RoutedEventArgs e)
        {
            string usergrouptxt = txtUsername.Text;
            try
            {
                if (string.IsNullOrEmpty(usergrouptxt))
                {
                    txtUsername.BorderBrush = new SolidColorBrush(Colors.Red);
                }
                else
                {

                }
            }
            catch (SqlException usrgrpexc)
            {
                MessageBox.Show(usrgrpexc.ToString());
            }

        }

How can I do the above operation in my ViewModel in MVVM?

Posted 25-Mar-13 20:28pm

Rahul Krishnan R

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Oleksandr Kulchytskyi · Answer 1 · 2013-03-25T22:19:00

Easily with help of MVVM Light Toolkit. and System.Windows.Interactivity from Blend SDK.
Just add this namespaces:

HTML

xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
xmlns:cmd="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras"

and then, in your TextBox XAML inject next lines:

HTML

<textbox x:name="txt1" ....="" xmlns:x="#unknown">
    <i:interaction.triggers xmlns:i="#unknown">
        <i:eventtrigger eventname="LostFocus">
            <cmd:eventtocommand command="{Binding TestCommand,<br mode=" hold=" />                                          Mode=OneWay}" xmlns:cmd="#unknown">
               CommandParameter="{Binding Text,
                                  ElementName=txt1,
                                  Mode=OneWay}"
               MustToggleIsEnabledValue="True" />
        </cmd:eventtocommand></i:eventtrigger>
    </i:interaction.triggers>
</textbox>