Сдал

WinForms/WinForms/FormMain.cs

@@ -68,7 +68,7 @@ namespace WinForms
             var service = Program.ServiceProvider?.GetService(typeof(FormOrder));
             if (!(service is FormOrder form)) return;
 
-            var selectedOrder = TreeView.GetNode(typeof(OrderBindingModel));//ошибка
+            var selectedOrder = TreeView.GetNode(typeof(OrderBindingModel));
 
             if (selectedOrder != null)
             {

WinForms/WinForms/FormOrder.cs

@@ -81,6 +81,7 @@ namespace WinForms
                 return;
             }
             string? amount = controlInputNullableInt1.Value.ToString();
+            if (controlInputNullableInt1.Value == null) amount = null;
 
             try
             {