diff --git a/SourceGen/WpfGui/EditLocalVariableTable.xaml b/SourceGen/WpfGui/EditLocalVariableTable.xaml
index 4458f54..471cdf7 100644
--- a/SourceGen/WpfGui/EditLocalVariableTable.xaml
+++ b/SourceGen/WpfGui/EditLocalVariableTable.xaml
@@ -48,28 +48,37 @@ limitations under the License.
         <TextBlock Grid.Column="0" Grid.Row="0" Grid.ColumnSpan="2" Margin="0,4,0,0"
                    Text="{Binding TableHeaderText, FallbackValue=Symbols defined in table at +######:}"/>
 
-        <ListView Name="symbolsListView" Grid.Column="0" Grid.Row="1" Margin="0,4,4,0"
-                  Height="300"
-                  FontFamily="{StaticResource GeneralMonoFont}"
+        <DataGrid Name="symbolsList" Grid.Column="0" Grid.Row="1" Margin="0,4,4,0"
+                  Width="582" Height="300"
                   ItemsSource="{Binding Variables}"
-                  SnapsToDevicePixels="True" SelectionMode="Single"
-                  SelectionChanged="SymbolsListView_SelectionChanged"
-                  MouseDoubleClick="SymbolsListView_MouseDoubleClick">
-            <ListView.Resources>
-                <Style TargetType="TextBlock">
-                    <Setter Property="TextTrimming" Value="CharacterEllipsis"/>
-                </Style>
-            </ListView.Resources>
-            <ListView.View>
-                <GridView AllowsColumnReorder="False">
-                    <GridViewColumn Header="Name" Width="118" DisplayMemberBinding="{Binding Label}"/>
-                    <GridViewColumn Header="Value" Width="72" DisplayMemberBinding="{Binding Value}"/>
-                    <GridViewColumn Header="Type" Width="45" DisplayMemberBinding="{Binding Type}"/>
-                    <GridViewColumn Header="Width" Width="45" DisplayMemberBinding="{Binding Width}"/>
-                    <GridViewColumn Header="Comment" Width="300" DisplayMemberBinding="{Binding Comment}"/>
-                </GridView>
-            </ListView.View>
-        </ListView>
+                  IsReadOnly="True"
+                  FontFamily="{StaticResource GeneralMonoFont}"
+                  SnapsToDevicePixels="True"
+                  GridLinesVisibility="Vertical"
+                  VerticalGridLinesBrush="#FF7F7F7F"
+                  AutoGenerateColumns="False"
+                  HeadersVisibility="Column"
+                  CanUserReorderColumns="False"
+                  SelectionMode="Single"
+                  SelectionChanged="SymbolsList_SelectionChanged"
+                  Sorting="SymbolsList_Sorting"
+                  MouseDoubleClick="SymbolsList_MouseDoubleClick">
+            <DataGrid.Resources>
+                <!-- make the no-focus color the same as the in-focus color -->
+                <!-- thanks: https://stackoverflow.com/a/13053511/294248 -->
+                <SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightBrushKey}"
+                                 Color="{x:Static SystemColors.HighlightColor}"/>
+                <SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightTextBrushKey}"
+                                 Color="{x:Static SystemColors.HighlightTextColor}"/>
+            </DataGrid.Resources>
+            <DataGrid.Columns>
+                <DataGridTextColumn Header="Name" Width="118" Binding="{Binding Label}"/>
+                <DataGridTextColumn Header="Value" Width="72" Binding="{Binding Value}"/>
+                <DataGridTextColumn Header="Type" Width="45" Binding="{Binding Type}"/>
+                <DataGridTextColumn Header="Width" Width="45" Binding="{Binding Width}"/>
+                <DataGridTextColumn Header="Comment" Width="300" Binding="{Binding Comment}"/>
+            </DataGrid.Columns>
+        </DataGrid>
 
         <StackPanel Grid.Column="1" Grid.Row="1">
             <Button Name="newSymbolButton" Width="120" Margin="4" Content="_New Symbol..."
diff --git a/SourceGen/WpfGui/EditLocalVariableTable.xaml.cs b/SourceGen/WpfGui/EditLocalVariableTable.xaml.cs
index 1e37638..20a0549 100644
--- a/SourceGen/WpfGui/EditLocalVariableTable.xaml.cs
+++ b/SourceGen/WpfGui/EditLocalVariableTable.xaml.cs
@@ -14,12 +14,14 @@
  * limitations under the License.
  */
 using System;
+using System.Collections;
 using System.Collections.ObjectModel;
 using System.ComponentModel;
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
 using System.Windows;
 using System.Windows.Controls;
+using System.Windows.Data;
 using System.Windows.Input;
 
 using Asm65;
@@ -46,18 +48,25 @@ namespace SourceGen.WpfGui {
             public string Label { get; private set; }
             public string Value { get; private set; }
             public string Type { get; private set; }
-            public string Width { get; private set; }
+            public int Width { get; private set; }
             public string Comment { get; private set; }
 
-            public FormattedSymbol(string label, string value, string type, string width,
-                    string comment) {
+            // Numeric form of Value, used so we can sort hex/dec/binary correctly.
+            public int NumericValue { get; private set; }
+
+            public FormattedSymbol(string label, int numericValue, string value, string type,
+                    int width, string comment) {
                 Label = label;
                 Value = value;
                 Type = type;
                 Width = width;
                 Comment = comment;
+
+                NumericValue = numericValue;
             }
         }
+
+        // List of items.  The Label is guaranteed to be unique.
         public ObservableCollection<FormattedSymbol> Variables { get; private set; } =
             new ObservableCollection<FormattedSymbol>();
 
@@ -141,7 +150,10 @@ namespace SourceGen.WpfGui {
                 mWorkTable = new LocalVariableTable();
             }
 
-            LoadVariables();
+            for (int i = 0; i < mWorkTable.Count; i++) {
+                DefSymbol defSym = mWorkTable[i];
+                Variables.Add(CreateFormattedSymbol(defSym));
+            }
         }
 
         public void Window_Loaded(object sender, RoutedEventArgs e) {
@@ -154,33 +166,106 @@ namespace SourceGen.WpfGui {
         /// <summary>
         /// Loads entries from the work table into the items source.
         /// </summary>
-        private void LoadVariables() {
-            Variables.Clear();
+        private FormattedSymbol CreateFormattedSymbol(DefSymbol defSym) {
+            string typeStr;
+            if (defSym.SymbolType == Symbol.Type.Constant) {
+                typeStr = Res.Strings.ABBREV_STACK_RELATIVE;
+            } else {
+                typeStr = Res.Strings.ABBREV_ADDRESS;
+            }
 
-            for (int i = 0; i < mWorkTable.Count; i++) {
-                DefSymbol defSym = mWorkTable[i];
-                string typeStr;
-                if (defSym.SymbolType == Symbol.Type.Constant) {
-                    typeStr = Res.Strings.ABBREV_STACK_RELATIVE;
-                } else {
-                    typeStr = Res.Strings.ABBREV_ADDRESS;
+            FormattedSymbol fsym = new FormattedSymbol(
+                defSym.Label,
+                defSym.Value,
+                mFormatter.FormatValueInBase(defSym.Value, defSym.DataDescriptor.NumBase),
+                typeStr,
+                defSym.DataDescriptor.Length,
+                defSym.Comment);
+            return fsym;
+        }
+
+        /// <summary>
+        /// Handles a Sorting event.  We need to sort by numeric value on the Value field, but
+        /// we want to use custom-formatted numeric values in multiple bases.
+        /// </summary>
+        private void SymbolsList_Sorting(object sender, DataGridSortingEventArgs e) {
+            DataGridColumn col = e.Column;
+
+            // Set the SortDirection to a specific value.  If we don't do this, SortDirection
+            // remains un-set, and the column header doesn't show up/down arrows or change
+            // direction when clicked twice.
+            ListSortDirection direction = (col.SortDirection != ListSortDirection.Ascending) ?
+                ListSortDirection.Ascending : ListSortDirection.Descending;
+            col.SortDirection = direction;
+
+            bool isAscending = direction != ListSortDirection.Descending;
+
+            IComparer comparer = new SymbolsListComparer(col.DisplayIndex, isAscending);
+            ListCollectionView lcv =
+                (ListCollectionView)CollectionViewSource.GetDefaultView(symbolsList.ItemsSource);
+            lcv.CustomSort = comparer;
+            e.Handled = true;
+        }
+
+        private class SymbolsListComparer : IComparer {
+            // Must match order of items in DataGrid.  DataGrid must not allow columns to be
+            // reordered.  We could check col.Header instead, but then we have to assume that
+            // the Header is a string that doesn't get renamed.
+            private enum SortField {
+                Label = 0, Value = 1, Type = 2, Width = 3, Comment = 4
+            }
+            private SortField mSortField;
+            private bool mIsAscending;
+
+            public SymbolsListComparer(int displayIndex, bool isAscending) {
+                Debug.Assert(displayIndex >= 0 && displayIndex <= 4);
+                mIsAscending = isAscending;
+                mSortField = (SortField)displayIndex;
+            }
+
+            // IComparer interface
+            public int Compare(object o1, object o2) {
+                FormattedSymbol fsym1 = (FormattedSymbol)o1;
+                FormattedSymbol fsym2 = (FormattedSymbol)o2;
+
+                // Sort primarily by specified field, secondarily by label (which should
+                // be unique).
+                int cmp;
+                switch (mSortField) {
+                    case SortField.Label:
+                        cmp = string.Compare(fsym1.Label, fsym2.Label);
+                        break;
+                    case SortField.Value:
+                        cmp = fsym1.NumericValue - fsym2.NumericValue;
+                        break;
+                    case SortField.Type:
+                        cmp = string.Compare(fsym1.Type, fsym2.Type);
+                        break;
+                    case SortField.Width:
+                        cmp = fsym1.Width - fsym2.Width;
+                        break;
+                    case SortField.Comment:
+                        cmp = string.Compare(fsym1.Comment, fsym2.Comment);
+                        break;
+                    default:
+                        Debug.Assert(false);
+                        return 0;
                 }
 
-                FormattedSymbol fsym = new FormattedSymbol(
-                    defSym.Label,
-                    mFormatter.FormatValueInBase(defSym.Value, defSym.DataDescriptor.NumBase),
-                    typeStr,
-                    defSym.DataDescriptor.Length.ToString(),
-                    defSym.Comment);
-
-                Variables.Add(fsym);
+                if (cmp == 0) {
+                    cmp = string.Compare(fsym1.Label, fsym2.Label);
+                }
+                if (!mIsAscending) {
+                    cmp = -cmp;
+                }
+                return cmp;
             }
         }
 
         private void UpdateControls() {
             // Enable or disable the edit/remove buttons based on how many items are selected.
             // (We're currently configured for single-select, so this is really just a != 0 test.)
-            int symSelCount = symbolsListView.SelectedItems.Count;
+            int symSelCount = symbolsList.SelectedItems.Count;
             removeSymbolButton.IsEnabled = (symSelCount == 1);
             editSymbolButton.IsEnabled = (symSelCount == 1);
         }
@@ -207,16 +292,17 @@ namespace SourceGen.WpfGui {
             }
         }
 
-        private void SymbolsListView_SelectionChanged(object sender, SelectionChangedEventArgs e) {
+        private void SymbolsList_SelectionChanged(object sender, SelectionChangedEventArgs e) {
             UpdateControls();
         }
 
-        private void SymbolsListView_MouseDoubleClick(object sender, MouseButtonEventArgs e) {
-            ListViewItem lvi = symbolsListView.GetClickedItem(e);
-            if (lvi == null) {
+        private void SymbolsList_MouseDoubleClick(object sender, MouseButtonEventArgs e) {
+            if (!symbolsList.GetClickRowColItem(e, out int unusedRow, out int unusedCol,
+                    out object objItem)) {
+                // Header or empty area; ignore.
                 return;
             }
-            FormattedSymbol item = (FormattedSymbol)lvi.Content;
+            FormattedSymbol item = (FormattedSymbol)objItem;
             DefSymbol defSym = mWorkTable.GetByLabel(item.Label);
             DoEditSymbol(defSym);
         }
@@ -229,19 +315,22 @@ namespace SourceGen.WpfGui {
                 Debug.WriteLine("ADD: " + dlg.NewSym);
                 mWorkTable.AddOrReplace(dlg.NewSym);
 
-                // Reload the contents.  This loses the selection, but that shouldn't be an
-                // issue when adding new symbols.  To do this incrementally we'd need to add
-                // the symbol at the correct sorted position.
-                LoadVariables();
+                // Add it to the display list, select it, and scroll it into view.
+                FormattedSymbol newItem = CreateFormattedSymbol(dlg.NewSym);
+                Variables.Add(newItem);
+                symbolsList.SelectedItem = newItem;
+                symbolsList.ScrollIntoView(newItem);
+
                 UpdateControls();
             }
         }
 
         private void EditSymbolButton_Click(object sender, EventArgs e) {
             // Single-select list view, button dimmed when no selection.
-            Debug.Assert(symbolsListView.SelectedItems.Count == 1);
-            FormattedSymbol item = (FormattedSymbol)symbolsListView.SelectedItems[0];
+            Debug.Assert(symbolsList.SelectedItems.Count == 1);
+            FormattedSymbol item = (FormattedSymbol)symbolsList.SelectedItems[0];
             DefSymbol defSym = mWorkTable.GetByLabel(item.Label);
+            Debug.Assert(defSym != null);
             DoEditSymbol(defSym);
         }
 
@@ -253,30 +342,43 @@ namespace SourceGen.WpfGui {
                 // Label might have changed, so remove old before adding new.
                 mWorkTable.RemoveByLabel(defSym.Label);
                 mWorkTable.AddOrReplace(dlg.NewSym);
-                LoadVariables();
+
+                // Replace entry in items source.
+                for (int i = 0; i < Variables.Count; i++) {
+                    if (Variables[i].Label.Equals(defSym.Label)) {
+                        Variables[i] = CreateFormattedSymbol(dlg.NewSym);
+                        break;
+                    }
+                }
+
                 UpdateControls();
             }
         }
 
         private void RemoveSymbolButton_Click(object sender, RoutedEventArgs e) {
             // Single-select list view, button dimmed when no selection.
-            Debug.Assert(symbolsListView.SelectedItems.Count == 1);
+            Debug.Assert(symbolsList.SelectedItems.Count == 1);
 
-            int selectionIndex = symbolsListView.SelectedIndex;
-            FormattedSymbol item = (FormattedSymbol)symbolsListView.SelectedItems[0];
+            int selectionIndex = symbolsList.SelectedIndex;
+            FormattedSymbol item = (FormattedSymbol)symbolsList.SelectedItems[0];
             mWorkTable.RemoveByLabel(item.Label);
-            LoadVariables();
+            for (int i = 0; i < Variables.Count; i++) {
+                if (Variables[i].Label.Equals(item.Label)) {
+                    Variables.RemoveAt(i);
+                    break;
+                }
+            }
             UpdateControls();
 
             // Restore selection to the item that used to come after the one we just deleted,
             // so you can hit "Remove" repeatedly to delete multiple items.
-            int newCount = symbolsListView.Items.Count;
+            int newCount = symbolsList.Items.Count;
             if (selectionIndex >= newCount) {
                 selectionIndex = newCount - 1;
             }
             if (selectionIndex >= 0) {
-                symbolsListView.SelectedIndex = selectionIndex;
-                removeSymbolButton.Focus();
+                symbolsList.SelectedIndex = selectionIndex;
+                removeSymbolButton.Focus();     // so you can keep banging on Enter
             }
         }
     }
diff --git a/SourceGen/WpfGui/EditProjectProperties.xaml b/SourceGen/WpfGui/EditProjectProperties.xaml
index 129653a..4ec0490 100644
--- a/SourceGen/WpfGui/EditProjectProperties.xaml
+++ b/SourceGen/WpfGui/EditProjectProperties.xaml
@@ -23,7 +23,7 @@ limitations under the License.
         xmlns:local="clr-namespace:SourceGen.WpfGui"
         mc:Ignorable="d"
         Title="Edit Project Properties"
-        Width="600" Height="400" ResizeMode="NoResize"
+        Width="640" Height="400" ResizeMode="NoResize"
         ShowInTaskbar="False" WindowStartupLocation="CenterOwner"
         Loaded="Window_Loaded">
 
@@ -146,26 +146,36 @@ limitations under the License.
                     <TextBlock Grid.Column="0" Grid.Row="0" Grid.ColumnSpan="2"
                                Margin="4,0,0,0" Text="Symbols defined in project:"/>
 
-                    <ListView Name="projectSymbolsListView" Grid.Column="0" Grid.Row="1" Margin="4,4,4,0"
-                              FontFamily="{StaticResource GeneralMonoFont}"
+                    <DataGrid Name="projectSymbolsList" Grid.Column="0" Grid.Row="1" Margin="4,4,4,0"
                               ItemsSource="{Binding ProjectSymbols}"
-                              SnapsToDevicePixels="True" SelectionMode="Single"
+                              IsReadOnly="True"
+                              FontFamily="{StaticResource GeneralMonoFont}"
+                              SnapsToDevicePixels="True"
+                              GridLinesVisibility="Vertical"
+                              VerticalGridLinesBrush="#FF7F7F7F"
+                              AutoGenerateColumns="False"
+                              HeadersVisibility="Column"
+                              CanUserReorderColumns="False"
+                              SelectionMode="Single"
                               SelectionChanged="List_SelectionChanged"
-                              MouseDoubleClick="ProjectSymbolsListView_MouseDoubleClick">
-                        <ListView.Resources>
-                            <Style TargetType="TextBlock">
-                                <Setter Property="TextTrimming" Value="CharacterEllipsis"/>
-                            </Style>
-                        </ListView.Resources>
-                        <ListView.View>
-                            <GridView AllowsColumnReorder="False">
-                                <GridViewColumn Header="Name" Width="118" DisplayMemberBinding="{Binding Label}"/>
-                                <GridViewColumn Header="Value" Width="72" DisplayMemberBinding="{Binding Value}"/>
-                                <GridViewColumn Header="Type" Width="45" DisplayMemberBinding="{Binding Type}"/>
-                                <GridViewColumn Header="Comment" Width="300" DisplayMemberBinding="{Binding Comment}"/>
-                            </GridView>
-                        </ListView.View>
-                    </ListView>
+                              Sorting="ProjectSymbolsList_Sorting"
+                              MouseDoubleClick="ProjectSymbolsList_MouseDoubleClick">
+                        <DataGrid.Resources>
+                            <!-- make the no-focus color the same as the in-focus color -->
+                            <!-- thanks: https://stackoverflow.com/a/13053511/294248 -->
+                            <SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightBrushKey}"
+                                 Color="{x:Static SystemColors.HighlightColor}"/>
+                            <SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightTextBrushKey}"
+                                 Color="{x:Static SystemColors.HighlightTextColor}"/>
+                        </DataGrid.Resources>
+                        <DataGrid.Columns>
+                            <DataGridTextColumn Header="Name" Width="118" Binding="{Binding Label}"/>
+                            <DataGridTextColumn Header="Value" Width="72" Binding="{Binding Value}"/>
+                            <DataGridTextColumn Header="Type" Width="45" Binding="{Binding Type}"/>
+                            <DataGridTextColumn Header="Width" Width="45" Binding="{Binding Width}"/>
+                            <DataGridTextColumn Header="Comment" Width="300" Binding="{Binding Comment}"/>
+                        </DataGrid.Columns>
+                    </DataGrid>
 
                     <StackPanel Grid.Column="1" Grid.Row="1">
                         <Button Name="newSymbolButton" Width="120" Margin="4" Content="_New Symbol..."
@@ -230,7 +240,7 @@ limitations under the License.
                     </Grid.RowDefinitions>
 
                     <TextBlock Grid.Column="0" Grid.Row="0" Margin="4,0,0,0"
-                               Text="Currently configured symbol files:"/>
+                               Text="Currently configured extension scripts:"/>
 
                     <ListBox Name="extensionScriptsListBox" Grid.Column="0" Grid.Row="1" Margin="4"
                              SelectionMode="Extended"
diff --git a/SourceGen/WpfGui/EditProjectProperties.xaml.cs b/SourceGen/WpfGui/EditProjectProperties.xaml.cs
index 81ec225..5594c67 100644
--- a/SourceGen/WpfGui/EditProjectProperties.xaml.cs
+++ b/SourceGen/WpfGui/EditProjectProperties.xaml.cs
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.ComponentModel;
@@ -23,6 +24,7 @@ using System.Runtime.CompilerServices;
 using System.Text;
 using System.Windows;
 using System.Windows.Controls;
+using System.Windows.Data;
 using System.Windows.Input;
 using Microsoft.Win32;
 
@@ -36,6 +38,8 @@ namespace SourceGen.WpfGui {
     /// Project properties dialog.
     /// </summary>
     public partial class EditProjectProperties : Window, INotifyPropertyChanged {
+        private const string NO_WIDTH_STR = "-";
+
         /// <summary>
         /// New set.  Updated when Apply or OK is hit.  This will be null if no changes have
         /// been applied.
@@ -169,7 +173,7 @@ namespace SourceGen.WpfGui {
             //
             // Enable or disable the edit/remove buttons based on how many items are selected.
             // (We're currently configured for single-select, so this is really just a != 0 test.)
-            int symSelCount = projectSymbolsListView.SelectedItems.Count;
+            int symSelCount = projectSymbolsList.SelectedItems.Count;
             removeSymbolButton.IsEnabled = (symSelCount == 1);
             editSymbolButton.IsEnabled = (symSelCount == 1);
 
@@ -401,13 +405,23 @@ namespace SourceGen.WpfGui {
             public string Label { get; private set; }
             public string Value { get; private set; }
             public string Type { get; private set; }
+            public string Width { get; private set; }
             public string Comment { get; private set; }
 
-            public FormattedSymbol(string label, string value, string type, string comment) {
+            // Numeric form of Value, used so we can sort hex/dec/binary correctly.
+            public int NumericValue { get; private set; }
+            public int NumericWidth { get; private set; }
+
+            public FormattedSymbol(string label, int numericValue, string value, string type,
+                    int numericWidth, string width, string comment) {
                 Label = label;
                 Value = value;
                 Type = type;
+                Width = width;
                 Comment = comment;
+
+                NumericValue = numericValue;
+                NumericWidth = numericWidth;
             }
         }
         public ObservableCollection<FormattedSymbol> ProjectSymbols { get; private set; } =
@@ -421,20 +435,121 @@ namespace SourceGen.WpfGui {
 
             foreach (KeyValuePair<string, DefSymbol> kvp in mWorkProps.ProjectSyms) {
                 DefSymbol defSym = kvp.Value;
-                string typeStr;
-                if (defSym.SymbolType == Symbol.Type.Constant) {
-                    typeStr = Res.Strings.ABBREV_CONSTANT;
-                } else {
-                    typeStr = Res.Strings.ABBREV_ADDRESS;
+                ProjectSymbols.Add(CreateFormattedSymbol(defSym));
+            }
+
+            // This doesn't seem to enable "live sorting".  It does an initial sort, but
+            // without calling the Sorting function.  I'm not sure what the point of this is,
+            // or how to cause the DataGrid to behave like somebody clicked on a header.
+
+            //ICollectionView view =
+            //    CollectionViewSource.GetDefaultView(projectSymbolsList.ItemsSource);
+            //SortDescriptionCollection sortDes = view.SortDescriptions;
+            //sortDes.Add(new SortDescription("Value", ListSortDirection.Descending));
+            //projectSymbolsList.Columns[0].SortDirection = ListSortDirection.Ascending;
+            //view.Refresh();
+        }
+
+        private FormattedSymbol CreateFormattedSymbol(DefSymbol defSym) {
+            string typeStr;
+            if (defSym.SymbolType == Symbol.Type.Constant) {
+                typeStr = Res.Strings.ABBREV_CONSTANT;
+            } else {
+                typeStr = Res.Strings.ABBREV_ADDRESS;
+            }
+
+            FormattedSymbol fsym = new FormattedSymbol(
+                defSym.Label,
+                defSym.Value,
+                mFormatter.FormatValueInBase(defSym.Value, defSym.DataDescriptor.NumBase),
+                typeStr,
+                defSym.DataDescriptor.Length,
+                defSym.HasWidth ? defSym.DataDescriptor.Length.ToString() : NO_WIDTH_STR,
+                defSym.Comment);
+            return fsym;
+        }
+
+        private void ProjectSymbolsList_Sorting(object sender, DataGridSortingEventArgs e) {
+            DataGridColumn col = e.Column;
+
+            // Set the SortDirection to a specific value.  If we don't do this, SortDirection
+            // remains un-set, and the column header doesn't show up/down arrows or change
+            // direction when clicked twice.
+            ListSortDirection direction = (col.SortDirection != ListSortDirection.Ascending) ?
+                ListSortDirection.Ascending : ListSortDirection.Descending;
+            col.SortDirection = direction;
+
+            bool isAscending = direction != ListSortDirection.Descending;
+
+            IComparer comparer = new ProjectSymbolComparer(col.DisplayIndex, isAscending);
+            ListCollectionView lcv = (ListCollectionView)
+                CollectionViewSource.GetDefaultView(projectSymbolsList.ItemsSource);
+            lcv.CustomSort = comparer;
+            e.Handled = true;
+        }
+
+        private class ProjectSymbolComparer : IComparer {
+            // Must match order of items in DataGrid.  DataGrid must not allow columns to be
+            // reordered.  We could check col.Header instead, but then we have to assume that
+            // the Header is a string that doesn't get renamed.
+            private enum SortField {
+                Label = 0, Value = 1, Type = 2, Width = 3, Comment = 4
+            }
+            private SortField mSortField;
+            private bool mIsAscending;
+
+            public ProjectSymbolComparer(int displayIndex, bool isAscending) {
+                Debug.Assert(displayIndex >= 0 && displayIndex <= 4);
+                mIsAscending = isAscending;
+                mSortField = (SortField)displayIndex;
+            }
+
+            // IComparer interface
+            public int Compare(object o1, object o2) {
+                FormattedSymbol fsym1 = (FormattedSymbol)o1;
+                FormattedSymbol fsym2 = (FormattedSymbol)o2;
+
+                // Sort primarily by specified field, secondarily by label (which should
+                // be unique).
+                int cmp;
+                switch (mSortField) {
+                    case SortField.Label:
+                        cmp = string.Compare(fsym1.Label, fsym2.Label);
+                        break;
+                    case SortField.Value:
+                        cmp = fsym1.NumericValue - fsym2.NumericValue;
+                        break;
+                    case SortField.Type:
+                        cmp = string.Compare(fsym1.Type, fsym2.Type);
+                        break;
+                    case SortField.Width:
+                        // The no-width case is a little weird, because the actual width will
+                        // be 1, but we want it to sort separately.
+                        if (fsym1.Width == fsym2.Width) {
+                            cmp = 0;
+                        } else if (fsym1.Width == NO_WIDTH_STR) {
+                            cmp = -1;
+                        } else if (fsym2.Width == NO_WIDTH_STR) {
+                            cmp = 1;
+                        } else {
+                            cmp = fsym1.NumericWidth - fsym2.NumericWidth;
+                        }
+                        break;
+                    case SortField.Comment:
+                        cmp = string.Compare(fsym1.Comment, fsym2.Comment);
+                        break;
+                    default:
+                        Debug.Assert(false);
+                        return 0;
                 }
 
-                FormattedSymbol fsym = new FormattedSymbol(
-                    defSym.Label,
-                    mFormatter.FormatValueInBase(defSym.Value, defSym.DataDescriptor.NumBase),
-                    typeStr,
-                    defSym.Comment);
-
-                ProjectSymbols.Add(fsym);
+                if (cmp == 0) {
+                    cmp = string.Compare(fsym1.Label, fsym2.Label);
+                }
+                if (!mIsAscending) {
+                    cmp = -cmp;
+                }
+                return cmp;
             }
         }
 
@@ -447,31 +562,31 @@ namespace SourceGen.WpfGui {
                 mWorkProps.ProjectSyms[dlg.NewSym.Label] = dlg.NewSym;
                 IsDirty = true;
 
-                // Reload the contents.  This loses the selection, but that shouldn't be an
-                // issue when adding new symbols.  To do this incrementally we'd need to add
-                // the symbol at the correct sorted position.
-                LoadProjectSymbols();
-                UpdateControls();
+                FormattedSymbol newItem = CreateFormattedSymbol(dlg.NewSym);
+                ProjectSymbols.Add(newItem);
+                projectSymbolsList.SelectedItem = newItem;
+                projectSymbolsList.ScrollIntoView(newItem);
 
+                UpdateControls();
                 okButton.Focus();
             }
         }
 
         private void EditSymbolButton_Click(object sender, EventArgs e) {
             // Single-select list view, button dimmed when no selection.
-            Debug.Assert(projectSymbolsListView.SelectedItems.Count == 1);
-            FormattedSymbol item = (FormattedSymbol)projectSymbolsListView.SelectedItems[0];
+            Debug.Assert(projectSymbolsList.SelectedItems.Count == 1);
+            FormattedSymbol item = (FormattedSymbol)projectSymbolsList.SelectedItems[0];
             DefSymbol defSym = mWorkProps.ProjectSyms[item.Label];
             DoEditSymbol(defSym);
         }
 
-        private void ProjectSymbolsListView_MouseDoubleClick(object sender,
-                MouseButtonEventArgs e) {
-            ListViewItem lvi = projectSymbolsListView.GetClickedItem(e);
-            if (lvi == null) {
+        private void ProjectSymbolsList_MouseDoubleClick(object sender, MouseButtonEventArgs e) {
+            if (!projectSymbolsList.GetClickRowColItem(e, out int unusedRow, out int unusedCol,
+                    out object objItem)) {
+                // Header or empty area; ignore.
                 return;
             }
-            FormattedSymbol item = (FormattedSymbol)lvi.Content;
+            FormattedSymbol item = (FormattedSymbol)objItem;
             DefSymbol defSym = mWorkProps.ProjectSyms[item.Label];
             DoEditSymbol(defSym);
         }
@@ -485,33 +600,46 @@ namespace SourceGen.WpfGui {
                 mWorkProps.ProjectSyms.Remove(defSym.Label);
                 mWorkProps.ProjectSyms[dlg.NewSym.Label] = dlg.NewSym;
                 IsDirty = true;
-                LoadProjectSymbols();
-                UpdateControls();
 
+                // Replace entry in items source.
+                for (int i = 0; i < ProjectSymbols.Count; i++) {
+                    if (ProjectSymbols[i].Label.Equals(defSym.Label)) {
+                        ProjectSymbols[i] = CreateFormattedSymbol(dlg.NewSym);
+                        break;
+                    }
+                }
+
+                UpdateControls();
                 okButton.Focus();
             }
         }
 
         private void RemoveSymbolButton_Click(object sender, RoutedEventArgs e) {
             // Single-select list view, button dimmed when no selection.
-            Debug.Assert(projectSymbolsListView.SelectedItems.Count == 1);
+            Debug.Assert(projectSymbolsList.SelectedItems.Count == 1);
 
-            int selectionIndex = projectSymbolsListView.SelectedIndex;
-            FormattedSymbol item = (FormattedSymbol)projectSymbolsListView.SelectedItems[0];
+            int selectionIndex = projectSymbolsList.SelectedIndex;
+            FormattedSymbol item = (FormattedSymbol)projectSymbolsList.SelectedItems[0];
             DefSymbol defSym = mWorkProps.ProjectSyms[item.Label];
             mWorkProps.ProjectSyms.Remove(defSym.Label);
             IsDirty = true;
-            LoadProjectSymbols();
+
+            for (int i = 0; i < ProjectSymbols.Count; i++) {
+                if (ProjectSymbols[i].Label.Equals(item.Label)) {
+                    ProjectSymbols.RemoveAt(i);
+                    break;
+                }
+            }
             UpdateControls();
 
             // Restore selection to the item that used to come after the one we just deleted,
             // so you can hit "Remove" repeatedly to delete multiple items.
-            int newCount = projectSymbolsListView.Items.Count;
+            int newCount = projectSymbolsList.Items.Count;
             if (selectionIndex >= newCount) {
                 selectionIndex = newCount - 1;
             }
             if (selectionIndex >= 0) {
-                projectSymbolsListView.SelectedIndex = selectionIndex;
+                projectSymbolsList.SelectedIndex = selectionIndex;
                 removeSymbolButton.Focus();
             }
         }
@@ -551,7 +679,7 @@ namespace SourceGen.WpfGui {
             }
             if (foundCount != 0) {
                 IsDirty = true;
-                LoadProjectSymbols();
+                LoadProjectSymbols();   // just reload the whole set
                 UpdateControls();
             }
 
diff --git a/SourceGen/WpfGui/MainWindow.xaml b/SourceGen/WpfGui/MainWindow.xaml
index eb3d227..fb36bdb 100644
--- a/SourceGen/WpfGui/MainWindow.xaml
+++ b/SourceGen/WpfGui/MainWindow.xaml
@@ -462,8 +462,9 @@ limitations under the License.
                 </GroupBox>
 
                 <GroupBox Grid.Row="2" Header="Notes">
-                    <DataGrid Name="notesGrid" IsReadOnly="True"
+                    <DataGrid Name="notesGrid"
                               ItemsSource="{Binding NotesList}"
+                              IsReadOnly="True"
                               FontFamily="{StaticResource GeneralMonoFont}"
                               SnapsToDevicePixels="True"
                               GridLinesVisibility="Vertical"
diff --git a/SourceGen/WpfGui/MainWindow.xaml.cs b/SourceGen/WpfGui/MainWindow.xaml.cs
index bdbf621..6ab6a59 100644
--- a/SourceGen/WpfGui/MainWindow.xaml.cs
+++ b/SourceGen/WpfGui/MainWindow.xaml.cs
@@ -1420,7 +1420,7 @@ namespace SourceGen.WpfGui {
             new ObservableCollection<ReferencesListItem>();
 
         private void ReferencesList_MouseDoubleClick(object sender, MouseButtonEventArgs e) {
-            if (!referencesGrid.GetClickRowColItem(e, out int rowIndex, out int colIndex,
+            if (!referencesGrid.GetClickRowColItem(e, out int unusedRow, out int unusedCol,
                     out object item)) {
                 // Header or empty area; ignore.
                 return;
@@ -1460,7 +1460,7 @@ namespace SourceGen.WpfGui {
             new ObservableCollection<NotesListItem>();
 
         private void NotesList_MouseDoubleClick(object sender, MouseButtonEventArgs e) {
-            if (!notesGrid.GetClickRowColItem(e, out int rowIndex, out int colIndex,
+            if (!notesGrid.GetClickRowColItem(e, out int unusedRow, out int unusedCol,
                     out object item)) {
                 // Header or empty area; ignore.
                 return;
@@ -1501,7 +1501,7 @@ namespace SourceGen.WpfGui {
             new ObservableCollection<SymbolsListItem>();
 
         private void SymbolsList_MouseDoubleClick(object sender, MouseButtonEventArgs e) {
-            if (!symbolsGrid.GetClickRowColItem(e, out int rowIndex, out int colIndex,
+            if (!symbolsGrid.GetClickRowColItem(e, out int unusedRow, out int unusedCol,
                     out object item)) {
                 // Header or empty area; ignore.
                 return;
@@ -1544,6 +1544,9 @@ namespace SourceGen.WpfGui {
         /// Handles a Sorting event.  We want to do a secondary sort on Name when one of the
         /// other columns is the primary sort key.
         /// </summary>
+        /// <remarks>
+        /// https://stackoverflow.com/a/2130557/294248
+        /// </remarks>
         private void SymbolsList_Sorting(object sender, DataGridSortingEventArgs e) {
             DataGridColumn col = e.Column;