Question

See I have this sample code

_service.GetCustomers((customers, error) =>
          {
             if (error != null)
             {                     
                MessageBox.Show(error.Message);
                return;
             }

             Customers = new ObservableCollection<CustomerViewModel>(customers);
             IsBusy = false;
          });

If I were to make a similar function call to another function which accepts more parameters how would that be. The function definition is like this

GetCustomers(DateTime sTime, int ID,  Action<IEnumerable<CustomerViewModel>, Exception> callback)

So how would the above function be invoked using the lambda expression?

Answer 1

The lambda expression is shorthand for an anonymous delegate which was introduced in C# 2.0 Action<T> and its siblings are generic delegates. Whenever you see an parameter of type Action<T> you can replace it with a lambda taking equivalent parameters. In this case it would be

service.GetCustomers(sometime, someId, (viewmodels, exception)=>{/*handle callback here*/});