Comboboxes in MVC from model driven ViewModel

❗🕜 Warning: this article may contain outdated information. Consider before using any descriptions/solutions, otherwise, it still can be helpful. Help: Synonyms and name changes


To get everything to work as described in the article, you must have the latest build (written 131108).

Combobox, picklist, or dropdown list – many names apply to the same thing.

The Combobox is perfect when setting references between objects – if the number of items to pick from is not too large. In the ViewModel Editor, you can decide how, and if, to handle How Null is represented in your picklist.

When creating the ViewModel, do this (look at the 2 last lines in the green ViewModelClass and the blue):

Comboboxes - 1.png

This is automated for you, if you want, by right-clicking:

Comboboxes - 2.png

Modlr knows that “Example1” is a perfect candidate for a Combobox since it is a single link.

You get this:

Comboboxes - 3.png

Modlr suggests Example1.allinstances be the pick list, but you are free to change it. Maybe you want to add a “->orderby(e|e.attribute1)” there.

To get the whole MVC roundtrip to work, we need to add an identity column to the PickListPresentation class.

Comboboxes - 4.png

Make sure CodeGen is checked and then generate code:

Comboboxes - 5.png

Looking at the generated code for the ViewModel VMExample2, we see this new thing:

Comboboxes - 6.png

Notice that modlr did not only add code for Example1, it also added code for Example1_AsExternalId… And this is important for MVC.

In the View, I enter this:

    <div class="display-field">
      @Html.DropDownListFor(x => x.Example1_AsExternalId, 
        new SelectList(Model.Example1_PickList , //The list
                       "Identity",               // What attribute to pick
                       "Presentation",           // what to present
                       Model.Example1_AsExternalId)) // what to set on pick
    </div>
    <div class="display-field">
            @Html.EditorFor(model => model.OwnedBy)    // Added this just for info   
    </div>

And I get this:

Comboboxes - 7.png

Then I change the combo and press save:

Comboboxes - 8.png

The save method does nothing special to make this happen:

        [HttpPost]
        public ActionResult Details(string Identity, VMExample2 offlinevm)
        {
          Example2 e2 = EcoSpace.ExternalIds.ObjectForId(Identity).AsObject as Example2;
          try
          {
            VMExample2 onlinevm=VMExample2.Create(EcoSpace, e2);
            ViewModelHelper.ApplyValues(offlinevm, onlinevm, null);
            Commit();
            return View("Details", onlinevm);
          }
          catch
          {
            return View("Details", offlinevm);
          }
        }

This page was edited 21 days ago on 02/10/2024. What links here