Enter Button Behavior

Question

Hi, I am using MVVM and would like to know how to create Enter Button Behavior. I need this for a search screen and be nice to just enter search criteria in textbox and hit ENTER instead of clicking the search button.  Thanks.

Answer 1

Here's what I use:

Imports System.Windows.Interactivity

Namespace Behaviors

    Public Class TextBoxUpdateBehavior : Inherits Behavior(Of TextBox)

        Public Sub New()

        End Sub

        Protected Overrides Sub OnAttached()
            MyBase.OnAttached()
            AddHandler AssociatedObject.TextChanged, AddressOf AssociatedObjectOnTextChanged
        End Sub

        Private Sub AssociatedObjectOnTextChanged(sender As Object, args As TextChangedEventArgs)

            Dim bindingExpr = AssociatedObject.GetBindingExpression(TextBox.TextProperty)
            bindingExpr.UpdateSource()

        End Sub

        Protected Overrides Sub OnDetaching()
            MyBase.OnDetaching()
            RemoveHandler AssociatedObject.TextChanged, AddressOf AssociatedObjectOnTextChanged
        End Sub


    End Class

End Namespace

Graeme

Answer 2

Hi, thanks for the reply, I'll have to translate it to C#.  How does it know which button to initiate the click on?

Answer 3

It fires a number of events that normally don't fire in MVVM. Here's how I hook up the textbox

            <TextBox Text="{Binding NewText, Mode=TwoWay}">
                <i:Interaction.Behaviors>
                    <behaviors:TextBoxUpdateBehavior/>
                </i:Interaction.Behaviors>
                <i:Interaction.Triggers>
                    <i:EventTrigger EventName="KeyUp">
                        <cmd:EventToCommand Command="{Binding KeyUpCommand}" PassEventArgsToCommand="True"/>
                    </i:EventTrigger>
                </i:Interaction.Triggers>
            </TextBox>

Then in the Codebehind (I use MVVMLight for Commands)

    Public ReadOnly Property KeyUpCommand As RelayCommand(Of KeyEventArgs)
        Get
            Return New RelayCommand(Of KeyEventArgs)(Sub(e)

                                                         If e.Key = Key.Enter Then
                                                             ' call the code that button would normally
                                                         End If

                                                     End Sub)
        End Get
    End Property

Graeme

Answer 4

Thanks, I will go ahead and give it a shot now.