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Outdated Comboboxes in MVC from model driven ViewModel

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Revision as of 09:01, 1 September 2020 by Christina (talk | contribs)

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❗🕜 Warning: this article may contain outdated information.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 in the article you need the latest build (written 131108)

Combobox, picklist or dropdown list – many names for 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 go like this (Look at the 2 last lines in the Green ViewModelClass and at 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 to 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

I 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 in the combo and press save:

Comboboxes - 8.png

The save method needs to do 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);
          }
        }