Moved detailsContent.DataContext assignation before Children.Add

src/Avalonia.Controls.DataGrid/DataGridRows.cs

@@ -2969,8 +2969,8 @@ private void UpdateRowDetailsHeightEstimate()
                 var detailsContent = RowDetailsTemplate.Build(dataItem);
                 if (detailsContent != null)
                 {
-                    _rowsPresenter.Children.Add(detailsContent);
                     detailsContent.DataContext = dataItem;
+                    _rowsPresenter.Children.Add(detailsContent);
                     detailsContent.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
                     RowDetailsHeightEstimate = detailsContent.DesiredSize.Height;
                     _rowsPresenter.Children.Remove(detailsContent);