TextBox's Text Property returns null when using CommandParameter

Question

I managed to create a Command, like so:

Code-behind

public static RoutedCommand GetValueCommand = new RoutedCommand();
private void ExecutedGetValueCommand(object sender, ExecutedRoutedEventArgs e)
{
    MessageBox.Show("Custom Command Executed");
    Button b = (sender) as Button;
    MessageBox.Show(b.CommandParameter.ToString());
}
private void CanExecuteGetValueCommand(object sender, CanExecuteRoutedEventArgs e)
{
    e.CanExecute = true;
}

XAML

<UserControl.CommandBindings>
    <CommandBinding Command="{x:Static local:ReturnsUserControl.GetValueCommand}"
                    Executed="ExecutedGetValueCommand"
                    CanExecute="CanExecuteGetValueCommand" />
</UserControl.CommandBindings>

<ListView>
    <ListView.View>
        <GridView>
            <GridViewColumn>
                <GridViewColumn.CellTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal"
                                    VerticalAlignment="Center"
                                    HorizontalAlignment="Center">
                            <TextBlock Text="{Binding ProductDescription}"/>
                         </StackPanel>
                    </DataTemplate>
                </GridViewColumn.CellTemplate>
            </GridViewColumn>
            <GridViewColumn>
                <GridViewColumn.CellTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal"
                                    VerticalAlignment="Center"
                                    HorizontalAlignment="Center">
                            <TextBox x:Name="txtExchangeQuantity"
                                     Tag="{Binding ProductBarcode}"/>
                            <Button Content="Add"
                                    Tag="{Binding ProductBarcode}"
                                    Command="{x:Static local:ReturnsUserControl.GetValueCommand}"
                                     CommandParameter="{Binding Text,ElementName=txtExchangeQuantity}"/>
                         </StackPanel>
                    </DataTemplate>
                </GridViewColumn.CellTemplate>
            </GridViewColumn>
        </GridView>
    </ListView.View>
</ListView>

When I clicked the button, CommandParameter always return null, even when I put something in the text box, and I'm sure that the command is working because Custom Command Executed shows.

What I want to achieve here is to get the value of the TextBox that has the same Tag value as the Button's Tag (same barcode), because there will be multiple instances of both the TextBox and the Button, and the Tag is the only one that can pair them.

Answer 1

As we spoke in the comments, you should be looking for ExecutedRoutedEventArgs.Parameter instead of checking the sender in your event handler.