Partially fixed Issue #22 - the EditableListBoxControl now accepts enter to add an item and retains focus in the text box after doing so.

Filtration/UserControls/EditableListBoxControl.xaml

@@ -41,7 +41,7 @@
                 <KeyBinding Key="Delete" Command="{Binding Path=DeleteItemCommand}" CommandParameter="{Binding ElementName=ControlListBox, Path=SelectedValue}" />
             </ListBox.InputBindings>
         </ListBox>
-        <toolkit:AutoCompleteBox Grid.Row="1" Grid.Column="0" ItemsSource="{Binding AutoCompleteItemsSource}" FilterMode="Contains" Text="{Binding AddItemText, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" />
+        <toolkit:AutoCompleteBox x:Name="AutoCompleteBox" Grid.Row="1" Grid.Column="0" ItemsSource="{Binding AutoCompleteItemsSource}" FilterMode="Contains" Text="{Binding AddItemText, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" PreviewKeyDown="AutoCompleteBox_OnPreviewKeyDown" />
         <Button Grid.Row="1" Grid.Column="1" Command="{Binding AddItemCommand}" IsDefault="True">Add</Button>
     </Grid>
 </UserControl>

Filtration/UserControls/EditableListBoxControl.xaml.cs

@@ -2,6 +2,8 @@
 using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Input;
 using Filtration.Annotations;
 using GalaSoft.MvvmLight.CommandWpf;
 
@@ -106,5 +108,13 @@ namespace Filtration.UserControls
             var handler = PropertyChanged;
             handler?.Invoke(this, new PropertyChangedEventArgs(propertyName));
         }
+
+        private void AutoCompleteBox_OnPreviewKeyDown(object sender, KeyEventArgs e)
+        {
+            if (e.Key == Key.Enter)
+            {
+                AddItemCommand.Execute(null);
+            }
+        }
     }
 }