Why does a command bound to a textbox not fire in wpf?

Question

I've bound the textbox to a command using the trigger but nothing appears to happen when the user hits enter on the keyboard. Why would that be? What I want to happen is when the user hits enter it appends the name to the list and clears the input field.

The main areas of focus are here: xaml snippet

   <TextBox Grid.Row="0" Text="{Binding InputText, UpdateSourceTrigger=PropertyChanged}">
            <TextBox.InputBindings>
                <KeyBinding Key="Enter" Command="{Binding Path=CmdSomething, UpdateSourceTrigger=PropertyChanged}"/>
            </TextBox.InputBindings>
        </TextBox>

and its calling this command in the main view model:

 public void CmdSomething()
        {
            Console.WriteLine(InputText);
        }

Below is the code for the entire project just in case someone needs it to test.

PROJECT CODE

VNodes.cs

namespace WpfApplication1
{
    public class VNode
    {
        public string Name { get; set; }
    }
}

MainWindow.xaml

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        xmlns:local="clr-namespace:WpfApplication1">

    <Window.DataContext>
        <local:MainViewModel/>
    </Window.DataContext>

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="30"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <TextBox Grid.Row="0" Text="{Binding InputText, UpdateSourceTrigger=PropertyChanged}">
            <TextBox.InputBindings>
                <KeyBinding Key="Enter" Command="{Binding Path=CmdSomething, UpdateSourceTrigger=PropertyChanged}"/>
            </TextBox.InputBindings>
        </TextBox>

        <ListBox Grid.Row="1" Background="LightBlue" ItemsSource="{Binding VNodes}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <WrapPanel>
                        <TextBlock Text="{Binding Name}" FontWeight="Bold" />
                    </WrapPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>
</Window>

MainViewModel

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.CompilerServices;
using System.Collections.ObjectModel;


namespace WpfApplication1
{
    public class MainViewModel : ObservableObject
    {
        private ObservableCollection<VNode> _vnodes;
        public ObservableCollection<VNode> VNodes
        {
            get { return _vnodes; }
            set
            {
                _vnodes = value;
                NotifyPropertyChanged("VNodes");
            }
        }

        private string _inputText = "";
        public string InputText
        {
            get { return _inputText; }
            set
            {
                if (value != _inputText)
                {
                    _inputText = value;
                }
            }
        }

        public void CmdSomething()
        {
            Console.WriteLine(InputText);
        }

        public MainViewModel()
        {
            //hard coded data for testing
            VNodes = new ObservableCollection<VNode>();
            List<string> names = new List<string>() { "Tammy", "Doug", "Mike", "Joey", "Leslie", "Emily", "Tom" };

            foreach(string name in names)
            {
                VNode item = new VNode();
                item.Name = name;
                VNodes.Add(item);
            }
        }
    }
}

ObservableObjects.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace WpfApplication1
{
    public class ObservableObject : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void NotifyPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

Answer 1

CmdSomething in your code is not a ICommand but instead just a function.

Now there are two ways to make it work in your case.

Create an ICommand. Wonderful tutorial.

If MyCommand is a property of type ICommand in your ViewModel, then to bind your Custom Command :

<TextBox.InputBindings>
      <KeyBinding Key="Enter" Command="{Binding MyCommand, Mode=OneWay}" />
</TextBox.InputBindings>

And if you want to call your function, then you can use CallMethodAction behavior. Discussion. You can search google for more tutorials.

For your current issue, this works without any issues whatsoever :

xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"

       <TextBox x:Name="textBox" Margin="144,80,288,0" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Height="32">
            <i:Interaction.Triggers>
                <ei:KeyTrigger Key="Return"> <!-- Note Blend Behaviors don't use Enter, instead use Return value -->
                    <ei:CallMethodAction TargetObject="{Binding DataContext, RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}}" MethodName="CmdSomething"/>
                </ei:KeyTrigger>
            </i:Interaction.Triggers>
        </TextBox>

Good discussion