Lite: add column-level filtering to all data grids (#18)

Lite/Controls/ColumnFilterPopup.xaml

@@ -0,0 +1,54 @@
+<UserControl x:Class="PerformanceMonitorLite.Controls.ColumnFilterPopup"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             Width="220"
+             FontFamily="Segoe UI">
+    <Border Background="{DynamicResource BackgroundBrush}" BorderBrush="{DynamicResource BorderBrush}" BorderThickness="1" CornerRadius="6" TextElement.FontFamily="Segoe UI">
+        <StackPanel Margin="12">
+            <!-- Header with column name -->
+            <TextBlock x:Name="HeaderText"
+                       Text="Filter Column"
+                       FontWeight="SemiBold"
+                       FontSize="13"
+                       Foreground="{DynamicResource ForegroundBrush}"
+                       Margin="0,0,0,12"/>
+
+            <!-- Operator dropdown -->
+            <TextBlock Text="Operator:"
+                       Foreground="{DynamicResource ForegroundDimBrush}"
+                       FontSize="11"
+                       Margin="0,0,0,4"/>
+            <ComboBox x:Name="OperatorComboBox"
+                      Height="28"
+                      Margin="0,0,0,12"
+                      SelectionChanged="OperatorComboBox_SelectionChanged"/>
+
+            <!-- Value input -->
+            <TextBlock x:Name="ValueLabel"
+                       Text="Value:"
+                       Foreground="{DynamicResource ForegroundDimBrush}"
+                       FontSize="11"
+                       Margin="0,0,0,4"/>
+            <TextBox x:Name="ValueTextBox"
+                     Height="28"
+                     Margin="0,0,0,16"
+                     Padding="6,0"
+                     VerticalContentAlignment="Center"
+                     KeyDown="ValueTextBox_KeyDown"/>
+
+            <!-- Buttons -->
+            <StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
+                <Button Content="Clear"
+                        Width="65"
+                        Height="28"
+                        Margin="0,0,8,0"
+                        Click="ClearButton_Click"/>
+                <Button Content="Apply"
+                        Width="65"
+                        Height="28"
+                        Click="ApplyButton_Click"
+                        IsDefault="True"/>
+            </StackPanel>
+        </StackPanel>
+    </Border>
+</UserControl>

Lite/Controls/ColumnFilterPopup.xaml.cs

@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2026 Erik Darling, Darling Data LLC
+ *
+ * This file is part of the SQL Server Performance Monitor Lite.
+ *
+ * Licensed under the MIT License. See LICENSE file in the project root for full license information.
+ */
+
+using System;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Input;
+using PerformanceMonitorLite.Models;
+
+namespace PerformanceMonitorLite.Controls;
+
+public partial class ColumnFilterPopup : UserControl
+{
+    private string _columnName = string.Empty;
+    private bool _suppressEvents = false;
+
+    public event EventHandler<FilterAppliedEventArgs>? FilterApplied;
+    public event EventHandler? FilterCleared;
+
+    public ColumnFilterPopup()
+    {
+        InitializeComponent();
+        PopulateOperatorComboBox();
+    }
+
+    private void PopulateOperatorComboBox()
+    {
+        OperatorComboBox.Items.Clear();
+
+        foreach (FilterOperator op in Enum.GetValues(typeof(FilterOperator)))
+        {
+            OperatorComboBox.Items.Add(new ComboBoxItem
+            {
+                Content = ColumnFilterState.GetOperatorDisplayName(op),
+                Tag = op
+            });
+        }
+
+        OperatorComboBox.SelectedIndex = 0;
+    }
+
+    public void Initialize(string columnName, ColumnFilterState? existingFilter)
+    {
+        _suppressEvents = true;
+        _columnName = columnName;
+        HeaderText.Text = $"Filter: {columnName}";
+
+        if (existingFilter != null && existingFilter.IsActive)
+        {
+            for (int i = 0; i < OperatorComboBox.Items.Count; i++)
+            {
+                if (OperatorComboBox.Items[i] is ComboBoxItem item && item.Tag is FilterOperator op)
+                {
+                    if (op == existingFilter.Operator)
+                    {
+                        OperatorComboBox.SelectedIndex = i;
+                        break;
+                    }
+                }
+            }
+
+            ValueTextBox.Text = existingFilter.Value;
+        }
+        else
+        {
+            OperatorComboBox.SelectedIndex = 0;
+            ValueTextBox.Text = string.Empty;
+        }
+
+        UpdateValueVisibility();
+        _suppressEvents = false;
+
+        ValueTextBox.Focus();
+        ValueTextBox.SelectAll();
+    }
+
+    private void OperatorComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
+    {
+        if (_suppressEvents) return;
+        UpdateValueVisibility();
+    }
+
+    private void UpdateValueVisibility()
+    {
+        var selectedOp = GetSelectedOperator();
+
+        bool showValue = selectedOp != FilterOperator.IsEmpty &&
+                        selectedOp != FilterOperator.IsNotEmpty;
+
+        ValueLabel.Visibility = showValue ? Visibility.Visible : Visibility.Collapsed;
+        ValueTextBox.Visibility = showValue ? Visibility.Visible : Visibility.Collapsed;
+    }
+
+    private FilterOperator GetSelectedOperator()
+    {
+        if (OperatorComboBox.SelectedItem is ComboBoxItem item && item.Tag is FilterOperator op)
+        {
+            return op;
+        }
+        return FilterOperator.Contains;
+    }
+
+    private void ValueTextBox_KeyDown(object sender, KeyEventArgs e)
+    {
+        if (e.Key == Key.Enter)
+        {
+            ApplyFilter();
+            e.Handled = true;
+        }
+        else if (e.Key == Key.Escape)
+        {
+            FilterCleared?.Invoke(this, EventArgs.Empty);
+            e.Handled = true;
+        }
+    }
+
+    private void ApplyButton_Click(object sender, RoutedEventArgs e)
+    {
+        ApplyFilter();
+    }
+
+    private void ApplyFilter()
+    {
+        var filterState = new ColumnFilterState
+        {
+            ColumnName = _columnName,
+            Operator = GetSelectedOperator(),
+            Value = ValueTextBox.Text.Trim()
+        };
+
+        FilterApplied?.Invoke(this, new FilterAppliedEventArgs { FilterState = filterState });
+    }
+
+    private void ClearButton_Click(object sender, RoutedEventArgs e)
+    {
+        ValueTextBox.Text = string.Empty;
+        OperatorComboBox.SelectedIndex = 0;
+
+        var filterState = new ColumnFilterState
+        {
+            ColumnName = _columnName,
+            Operator = FilterOperator.Contains,
+            Value = string.Empty
+        };
+
+        FilterCleared?.Invoke(this, EventArgs.Empty);
+        FilterApplied?.Invoke(this, new FilterAppliedEventArgs { FilterState = filterState });
+    }
+}
+
+public class FilterAppliedEventArgs : EventArgs
+{
+    public ColumnFilterState FilterState { get; set; } = new ColumnFilterState();
+}