Issue 14204 fix data grid view excessive cpu+memory usage

src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridView.Methods.cs

@@ -25593,6 +25593,23 @@ private void ReleaseMouse()
         Capture = false;
     }
 
+    private static void ReleaseRowUiaProviders(DataGridViewRow row)
+    {
+        if (!row.IsAccessibilityObjectCreated)
+        {
+            return;
+        }
+
+        DataGridViewCellCollection cells = row.Cells;
+        for (int cellIndex = 0; cellIndex < cells.Count; cellIndex++)
+        {
+            cells[cellIndex].ReleaseUiaProvider();
+        }
+
+        row.HeaderCell.ReleaseUiaProvider();
+        row.ReleaseUiaProvider();
+    }
+
     internal override void ReleaseUiaProvider(HWND handle)
     {
         if (!IsAccessibilityObjectCreated)
@@ -25602,17 +25619,22 @@ internal override void ReleaseUiaProvider(HWND handle)
 
         if (OsVersion.IsWindows8OrGreater())
         {
-            foreach (DataGridViewRow row in Rows)
+            // Collect unique rows from SharedList using HashSet for deduplication.
+            // SharedList may have several hundred thousand entries, but most point to the same shared row instances.
+            HashSet<DataGridViewRow> uniqueRows = [];
+            List<DataGridViewRow> sharedList = Rows.SharedList;
+            for (int i = 0; i < sharedList.Count; i++)
             {
-                foreach (DataGridViewCell cell in row.Cells)
-                {
-                    cell.ReleaseUiaProvider();
-                }
+                uniqueRows.Add(sharedList[i]);
+            }
 
-                row.HeaderCell.ReleaseUiaProvider();
-                row.ReleaseUiaProvider();
+            // Release UIA providers for unique rows
+            foreach (DataGridViewRow row in uniqueRows)
+            {
+                ReleaseRowUiaProviders(row);
             }
 
+            // Release column header accessibility objects
             foreach (DataGridViewColumn column in Columns)
             {
                 column.HeaderCell.ReleaseUiaProvider();
@@ -25621,7 +25643,6 @@ internal override void ReleaseUiaProvider(HWND handle)
             _editingPanel?.ReleaseUiaProvider(HWND.Null);
             _editingPanelAccessibleObject = null;
             _topLeftHeaderCell?.ReleaseUiaProvider();
-
             if (AccessibilityObject is DataGridViewAccessibleObject accessibleObject)
             {
                 accessibleObject.ReleaseChildUiaProviders();

src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewColumnCollection.cs

@@ -1064,7 +1064,16 @@ internal void RemoveAtInternal(int index, bool force)
 
         if (DataGridView.IsAccessibilityObjectCreated && OsVersion.IsWindows8OrGreater())
         {
-            foreach (DataGridViewRow row in DataGridView.Rows)
+            // Collect unique rows from SharedList using HashSet for deduplication.
+            HashSet<DataGridViewRow> uniqueRows = [];
+            List<DataGridViewRow> sharedList = DataGridView.Rows.SharedList;
+            for (int i = 0; i < sharedList.Count; i++)
+            {
+                uniqueRows.Add(sharedList[i]);
+            }
+
+            // Release UIA providers for the cell at the removed column index
+            foreach (DataGridViewRow row in uniqueRows.Where(row => row.IsAccessibilityObjectCreated))
             {
                 row.Cells[index].ReleaseUiaProvider();
             }

src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewRow.DataGridViewRowAccessibleObject.cs

@@ -26,16 +26,6 @@ public DataGridViewRowAccessibleObject(DataGridViewRow owner)
             _owningDataGridViewRow = owner;
         }
 
-        /// <summary>
-        ///  Returns the index of the row, taking into account the invisibility of other rows.
-        /// </summary>
-        private int VisibleIndex
-            => _owningDataGridViewRow?.DataGridView is DataGridView dataGridView
-                ? dataGridView.ColumnHeadersVisible
-                    ? dataGridView.Rows.GetVisibleIndex(_owningDataGridViewRow) + 1
-                    : dataGridView.Rows.GetVisibleIndex(_owningDataGridViewRow)
-                : -1;
-
         public override Rectangle Bounds
         {
             get
@@ -338,35 +328,39 @@ dataGridView.CurrentCell is not null &&
             {
                 case AccessibleNavigation.Down:
                 case AccessibleNavigation.Next:
-                    if (_owningDataGridViewRow.Index != _owningDataGridViewRow.DataGridView.Rows.GetLastRow(DataGridViewElementStates.Visible))
-                    {
-                        int visibleIndex = VisibleIndex;
-                        return visibleIndex < 0
-                            ? null
-                            : _owningDataGridViewRow.DataGridView.AccessibilityObject.GetChild(visibleIndex + 1);
-                    }
-                    else
+                    DataGridView dataGridView = _owningDataGridViewRow.DataGridView;
+                    int nextDisplayed = dataGridView.Rows.GetNextRow(_owningDataGridViewRow.Index, DataGridViewElementStates.Displayed);
+                    if (nextDisplayed == -1)
                     {
                         return null;
                     }
 
+                    return dataGridView.Rows[nextDisplayed].AccessibilityObject;
+
                 case AccessibleNavigation.Up:
                 case AccessibleNavigation.Previous:
-                    if (_owningDataGridViewRow.Index != _owningDataGridViewRow.DataGridView.Rows.GetFirstRow(DataGridViewElementStates.Visible))
-                    {
-                        return _owningDataGridViewRow.DataGridView.AccessibilityObject.GetChild(VisibleIndex - 1);
-                    }
-                    else if (_owningDataGridViewRow.DataGridView.ColumnHeadersVisible)
+                    dataGridView = _owningDataGridViewRow.DataGridView;
+                    int current = _owningDataGridViewRow.Index;
+                    int previousDisplayed = dataGridView.Rows.GetPreviousRow(current, DataGridViewElementStates.Displayed);
+                    if (previousDisplayed != -1)
                     {
-                        // return the top row header acc obj
-                        return ParentPrivate?.GetChild(0);
+                        return _owningDataGridViewRow.DataGridView.Rows[previousDisplayed].AccessibilityObject;
                     }
-                    else
+
+                    if (_owningDataGridViewRow.DataGridView.RowHeadersVisible)
                     {
-                        // if this is the first row and the DataGridView RowHeaders are not visible return null;
-                        return null;
+                        var headerCell = _owningDataGridViewRow.DataGridView.Rows[current].HeaderCell;
+                        if (headerCell is not null)
+                        {
+                            // Directly return the row header cell's AccessibleObject.
+                            // This avoids container child-index access (no GetChild(i)).
+                            return headerCell.AccessibilityObject;
+                        }
                     }
 
+                    // if this is the first row and the DataGridView RowHeaders are not visible return null;
+                    return null;
+
                 case AccessibleNavigation.FirstChild:
                     if (GetChildCount() == 0)
                     {