Repro code for #292

ValidCode.Netcore/Repro/Issue292.cs

@@ -0,0 +1,68 @@
+namespace ValidCode.Repro
+{
+    using System.Collections;
+    using System.Collections.ObjectModel;
+    using System.Windows;
+    using System.Windows.Controls;
+
+    public static class Issue292
+    {
+        /// <summary>
+        /// An <see cref="IEnumerable"/> of rows where each row is an <see cref="IEnumerable"/> with the values.
+        /// </summary>
+        public static readonly DependencyProperty EnumerableProperty = DependencyProperty.RegisterAttached(
+            "Enumerable",
+            typeof(IEnumerable),
+            typeof(Issue292),
+            new PropertyMetadata(default(IEnumerable)));
+
+        /// <summary>Helper for setting <see cref="EnumerableProperty"/> on <paramref name="element"/>.</summary>
+        /// <param name="element"><see cref="DataGrid"/> to set <see cref="EnumerableProperty"/> on.</param>
+        /// <param name="value">RowsSource property value.</param>
+        public static void SetEnumerable(this DataGrid element, IEnumerable? value)
+        {
+            if (element is null)
+            {
+                throw new System.ArgumentNullException(nameof(element));
+            }
+
+            element.SetValue(EnumerableProperty, value);
+        }
+
+        /// <summary>Helper for getting <see cref="EnumerableProperty"/> from <paramref name="element"/>.</summary>
+        /// <param name="element"><see cref="DataGrid"/> to read <see cref="EnumerableProperty"/> from.</param>
+        /// <returns>RowsSource property value.</returns>
+        [AttachedPropertyBrowsableForChildren(IncludeDescendants = false)]
+        [AttachedPropertyBrowsableForType(typeof(DataGrid))]
+        public static IEnumerable? GetEnumerable(this DataGrid element)
+        {
+            if (element is null)
+            {
+                throw new System.ArgumentNullException(nameof(element));
+            }
+
+            return (IEnumerable)element.GetValue(EnumerableProperty);
+        }
+
+        public static DataGrid M1()
+        {
+            var dataGrid = new DataGrid();
+            var xs = new ObservableCollection<int>(new[] { 1, 2 });
+            dataGrid.SetValue(Issue292.EnumerableProperty, xs);
+            return dataGrid;
+        }
+
+        public static DataGrid M2()
+        {
+            var dataGrid = new DataGrid();
+            var xs = new ObservableCollection<ObservableCollection<int>>
+            {
+                new ObservableCollection<int>(new[] { 1, 2 }),
+                new ObservableCollection<int>(new[] { 3, 4 }),
+                new ObservableCollection<int>(new[] { 5, 6 }),
+            };
+            dataGrid.SetValue(Issue292.EnumerableProperty, xs);
+            return dataGrid;
+        }
+    }
+}