Set DataGridCollectionView.Filter after grid attach

Object-initializer Filter assignment lands on the DataGridCollectionView
instance but is gone by the time the grid finishes wiring it up — the
live view ends up with Filter=null, so Refresh() returns the unfiltered
source. Construct the view first, attach to the grid, then assign Filter
so the predicate sticks. The verification oracle now asserts on the
view's Count (the actual visible-row count) rather than re-running the
predicate manually, which catches this exact regression.

Assisted-by: Claude:claude-opus-4-7:Claude Code

ILSpy.Tests/Metadata/MetadataFilterRowVerificationTest.cs

@@ -21,6 +21,7 @@ using System.Diagnostics;
 using System.Linq;
 using System.Threading.Tasks;
 
+using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.Headless.NUnit;
 using Avalonia.Threading;
@@ -108,24 +109,32 @@ public class MetadataFilterRowVerificationTest
 		var totalRows = page.Items.Count;
 		totalRows.Should().BeGreaterThan(0, "TypeDef must have rows for filtering to be observable");
 
+		// The DataGrid's ItemsSource is the DataGridCollectionView wired up by ApplySchema.
+		// Its Count reflects what the user actually sees on screen — that's the post-filter
+		// row count we need to assert on, not the predicate evaluated on raw Items.
+		var view = grid.ItemsSource as DataGridCollectionView;
+		view.Should().NotBeNull("the metadata grid must expose a DataGridCollectionView so the per-column filter can re-evaluate");
+		view!.Count.Should().Be(totalRows, "every row should be visible before any filter is set");
+
 		// === STEP 6: Type "System" into the rendered TextBox ===
 		headerBox!.Text = "System";
 		Dispatcher.UIThread.RunJobs();
 		nameFilter.Text.Should().Be("System",
 			"setting the rendered TextBox.Text must propagate to ColumnFilter.Text");
-		var visibleByPredicate = page.Items.Count(e => MetadataTablePageModel.MatchesFilters(e, page.ColumnFilters));
-		visibleByPredicate.Should().BeLessThan(totalRows,
-			"the predicate must hide at least one TypeDef row when filtering Name on 'System'");
-		TestContext.Out.WriteLine($"[VERIFY] After typing 'System': filter='{nameFilter.Text}' visible={visibleByPredicate}/{totalRows}");
+
+		var expectedVisible = page.Items.Count(e => MetadataTablePageModel.MatchesFilters(e, page.ColumnFilters));
+		expectedVisible.Should().BeLessThan(totalRows,
+			"the predicate must hide at least one TypeDef row when Name contains 'System'");
+		view.Count.Should().Be(expectedVisible,
+			"the live grid view must reflect the filter — typing into the header must shrink the visible-row set, not just update ColumnFilter.Text");
 		window.CaptureAndShow(label: "step6_typed_System");
 
 		// === STEP 7: Clear the filter ===
 		headerBox.Text = "";
 		Dispatcher.UIThread.RunJobs();
 		nameFilter.Text.Should().BeEmpty("clearing the TextBox must clear the filter");
-		var visibleAfterClear = page.Items.Count(e => MetadataTablePageModel.MatchesFilters(e, page.ColumnFilters));
-		visibleAfterClear.Should().Be(totalRows, "an empty filter must show every row again");
-		TestContext.Out.WriteLine($"[VERIFY] After clearing: filter='{nameFilter.Text}' visible={visibleAfterClear}/{totalRows}");
+		view.Count.Should().Be(totalRows,
+			"clearing the filter must restore every row in the visible grid view");
 		window.CaptureAndShow(label: "step7_cleared");
 	}
 }

ILSpy/Views/MetadataTablePage.axaml.cs

@@ -171,10 +171,13 @@ namespace ILSpy.Views
 			foreach (var c in boundModel.Columns)
 				grid.Columns.Add(c);
 			var model = boundModel;
-			itemsView = new DataGridCollectionView(model.Items) {
-				Filter = item => MetadataTablePageModel.MatchesFilters(item, model.ColumnFilters),
-			};
+			itemsView = new DataGridCollectionView(model.Items);
 			grid.ItemsSource = itemsView;
+			// Assign Filter AFTER attaching to the grid; the DataGridCollectionView's setter
+			// short-circuits on _filter == value and an object-initializer assignment seems to
+			// land on a transient state that the grid replaces, so the filter ends up null
+			// on the live view by the time refresh requests come in.
+			itemsView.Filter = item => MetadataTablePageModel.MatchesFilters(item, model.ColumnFilters);
 		}
 
 		void ApplyScrollTarget()