Using ASP.NET MVC, how to best avoid writing both the Add View and Edit View?

Question

The Add view and the Edit view are often incredibly similar that it is unwarranted to write 2 views. As the app evolves you would be making the same changes to both.

However, there are usually subtle differences. For instance, a field might be read-only once it's been added, and if that field is a DropDownList you no longer need that List in the ViewData.

So, should I create a view data class which contains all the information for both views, where, depending on the operation you're performing, certain properties will be null?
Should I include the operation in the view data as an enum?
Should I surround all the subtle differences with <% if( ViewData.Model.Op == Ops.Editing ) { %> ?

Or is there a better way?

Answer 1

It's pretty easy really. Let's assume you're editing a blog post.

Here's your 2 actions for new/edit:

public class BlogController : Controller
{
   public ActionResult New()
   {
      var post = new Post();
      return View("Edit", post);
   }

   public ActionResult Edit(int id)
   {
      var post = _repository.Get(id);
      return View(post);
   }

   ....

}

And here's the view:

<% using(Html.Form("save")) { %>
<%= Html.Hidden("Id") %>

<label for="Title">Title</label>
<%= Html.TextBox("Title") %>

<label for="Body">Body</label>
<%= Html.TextArea("Body") %>

<%= Html.Submit("Submit") %>
<% } %>

And here's the Save action that the view submits to:

public ActionResult Save(int id, string title, string body)
{
   var post = id == 0 ? new Post() : _repository.Get(id);
   post.Title = title;
   post.Body = body;

   _repository.Save(post);

   return RedirectToAction("list");
}