How can I use the DRY principle in ASP.NET MVC to refactor this code?

Question

I have several methods in one of my controllers that does this:

ViewData["Customers"] = LoadCustomers(); ViewData["Employees"] = LoadEmployees(); ViewData["Statuses"] = LoadStatuses(); etc...... 

Here's LoadCustomers (), but LoadEmployees, LoadStatuses, and everyone else are pretty much the same logic:

 private static SelectList LoadCustomers() { IList<Customer> customers; try { IServiceCallService scService = new ServiceCallService(); customers = scService.GetCustomers(); Customer c = new Customer { ID = "", Name = "-- Select a Facility --" }; customers.Insert(0, c); } catch { customers = new List<Customer>(); Customer c = new Customer { ID = "", Name = "-- No Facilities on File --" }; customers.Insert(0, c); } return new SelectList(customers, "ID", "Name"); } 

How can I write this code better, so I don’t need a new method every time I add a new selection list?

Answer 1

Seems like this might be a good candidate for generics:

 private static SelectList LoadItems<T>() where T : new, ... { // Add any additional interfaces // that need to be supported by T // for your Load method to work, // as appropriate. IList<T> items; try { IServiceCallService scService = new ServiceCallService(); results = scService.Get<T>(); // You'll need to replace GetCustomers() with // a generic Get<T> method. // ... } catch // Really needed? What are you trying to catch here? (This catches { // everything silently. I suspect this is overkill.) // ... } return new SelectList(items, "ID", "Name"); } 

Answer 2

You can also try a more functional approach.

 public IList<T> Load<T>(Func<IList<T>> getList, T prependItem) { var list = getList(); list.Insert(0, prependItem); return list; } 

Using:

 var prependItem = new Customer { ID = "", Name = "-- Select a Facility --" }; ViewData["Customers"] = new SelectList( Load(new ServiceCallService().GetCustomers(), prependItem), "ID", "Name"); 

This approach also separates list building from the details of what is being built - SelectList.

Answer 3

I would go even further and write this in the controller code:

  ViewData["Customers"] = new SelectList( new ServiceCallService().GetCustomers(), "ID","Name") 

and it looks

 <%= Html.DropDownList("Customers", ((SelectList)ViewData["Customers"]).Count() > 0 ? "-- Select a Facility --" : "-- No Facilities on File --" ) %>