How to return error from a plugin

Hi, I'm coding a plugin that implements IConsumer EntityInserted<ShoppingCartItem>

When a product is inserted in the cart I check if the current avaiability is bigger or equal to the requested quantity.

public void HandleEvent(EntityInserted<ShoppingCartItem> eventMessage)
    {
         int quantity = eventMessage.Entity.Quantity;
         int avaiableQuantity= _REQUEST_TO_WEB_SERVICE;
         if(quantity > avaiableQuantity)
         {
              WANT TO SHOW ERROR TO THE USER AND 
              SET QUANTITY to avaiableQuantity

         }
   }         

How can I show an error to the user?
Is ok to lower the ShoppingCartItem quantity setting

eventMessage.Entity.Quantity = avaiableQuantity;

?
Thank you very much.

throw new ArgumentNullException("filterContext");

Hi, I'm coding a plugin that implements IConsumer EntityInserted<ShoppingCartItem>

When a product is inserted in the cart I check if the current avaiability is bigger or equal to the requested quantity.

public void HandleEvent(EntityInserted<ShoppingCartItem> eventMessage)
    {
         int quantity = eventMessage.Entity.Quantity;
         int avaiableQuantity= _REQUEST_TO_WEB_SERVICE;
         if(quantity > avaiableQuantity)
         {
              WANT TO SHOW ERROR TO THE USER AND 
              SET QUANTITY to avaiableQuantity

         }
   }         

How can I show an error to the user?
Is ok to lower the ShoppingCartItem quantity setting

eventMessage.Entity.Quantity = avaiableQuantity;

?
Thank you very much.

ErrorNotification(_localizationService.GetResource("your.customer.error.message"), true);

Hi, I'm coding a plugin that implements IConsumer EntityInserted<ShoppingCartItem>

When a product is inserted in the cart I check if the current avaiability is bigger or equal to the requested quantity.

public void HandleEvent(EntityInserted<ShoppingCartItem> eventMessage)
    {
         int quantity = eventMessage.Entity.Quantity;
         int avaiableQuantity= _REQUEST_TO_WEB_SERVICE;
         if(quantity > avaiableQuantity)
         {
              WANT TO SHOW ERROR TO THE USER AND 
              SET QUANTITY to avaiableQuantity

         }
   }         

How can I show an error to the user?
Is ok to lower the ShoppingCartItem quantity setting

eventMessage.Entity.Quantity = avaiableQuantity;

?
Thank you very much.


You can use following method in your plugin/controller for friendly error messagebox showing.

ErrorNotification(_localizationService.GetResource("your.customer.error.message"), true);