Fix order of operations bug in DataGrid SelectItem and SelectCell. (#464)

Co-authored-by: atanas.popatanasov <[email protected]>

Author: APopatanasov

Controls/Grid/Grid.UWP/View/RadDataGrid.Selection.cs

@@ -126,9 +126,9 @@ SelectionService ISelectionService.SelectionService
         /// In order to select a Row, the <see cref="SelectionUnit"/> value should be <c>DataGridSelectionUnit.Row</c>.
         /// </remarks>
         public void SelectItem(object item)
-        {
-            this.selectionService.SelectItem(item, true, false);
+        {
             this.UpdateItemToSelectFrom(item);
+            this.selectionService.SelectItem(item, true, false);
         }
 
         /// <summary>
@@ -158,8 +158,8 @@ public void DeselectItem(object item)
         /// </remarks>
         public void SelectCell(DataGridCellInfo item)
         {
-            this.selectionService.SelectCellInfo(item, true, false);
             this.UpdateItemToSelectFrom(item);
+            this.selectionService.SelectCellInfo(item, true, false);
         }
 
         /// <summary>