Validating a drop down list in MVC3?

Question

I'm working in MVC3 with Entity Framework. I've got an entity called Product that has two properties I'd like to validate when a user adds a new record. To do this, I've created a buddy class, as so:

using System;
using System.ComponentModel.DataAnnotations;

namespace Rpm.Data.Partials
{
    [MetadataType(typeof(ProductMetadata))]
    public partial class Product
    {
    }
}

The metadata class is as so:

using System;
using System.ComponentModel.DataAnnotations;

namespace Rpm.Data.Partials
{
    public class ProductMetadata
    {
        [Required]
        public string ProductName { get; set; }

        [Range(200, 1000, ErrorMessage = "You must select a valid Account Type")]
        public int AccountTypeId { get; set; }
    }
}

The view that allows users to add a new record is like this:

@model Rpm.Data.Product

@{
    ViewBag.Title = "Product"
}

<script type="text/javascript">
    $(document).ready(function() {
        //There should be no selection in the drop-down box when the form is first displayed.
        document.getElementsByTagName("select")[0].selectedIndex = -1;
    }

    function formSubmit() {
        var form = $("form");

        if (form.valid()) {
            (event.preventDefault) ? event.preventDefault() : event.returnValue = false;
            document.getElementById("frmNewProduct").submit();
            return true;
        }
        else {
            return false;
        }
    }
</script>

<h2>Add New Product</h2>

@using (Html.BeginForm("Create", "Product", new { id = new Product() }, FormMethod.Post, new { id = "frmNewProduct" }))
{
    @Html.ValidationSummary(true)
    <table>
        <tr>
            <td>
                Product Name
            </td>
            <td>
                @Html.TextBoxFor(m => new Product().ProductName)
                @Html.ValidationMessageFor(m => new Product().AccountTypeId)
            </td>
        </tr>
        <tr>
            <td>
                Account Type
            </td>
            <td>
                @Html.DropDownListFor(m => new Product().AccountTypeId, new SelectList(Lookup.Instance.AccountTypes, "AccountTypeId", "AccountTypeName"))
                @Html.ValidationMessageFor(m => new Product().AccountTypeId)
            </td>
        </tr>
        <tr>
            <td />
            <td>
                <input type="image" src="@Url.Content("~/Content/images/savebutton.png")" onclick="return formSubmit()" />
            </td>
        </tr>
    </table>
}

(Of course, the above is quite simplified just to avoid overloading the post with code that's not really relevant.)

The problem is that, when the user clicks the Save button, the validation for the ProductName fires just fine and displays the validation message if the field is blank; however, the message for AccountTypeId is never displayed, even if the drop-down is left without a selection (selectedIndex == -1). I know the RangeAttribute on AccountTypeId is being picked up, because when EF tries to save changes to the entities, it throws a DbEntityValidationException, and the text of the ErrorMessage is the custom error message I specified in the metadata. I just can't seem to get it to display on the page and cause the form to fail validation, preventing the user from saving.

Any suggestions as to what I'm doing wrong would be most appreciated!

TIA,

Jeff

Erik Funkenbusch · Accepted Answer · 2012-02-06 23:38:22Z

2

When you do this:

@Html.TextBoxFor(m => new Product().ProductName) 
@Html.ValidationMessageFor(m => new Product().AccountTypeId)

You're create two entirely different Product() instances, and you create additional Product instances for each property. this might work, since MVC is just using the lambda to create a layout format, but it's in general not very efficient and wastes memory.

Your model type is already product. You should just be using m => m.ProductName

This might be confusing the validation system. I'd just do as I suggest and see if the problem continues.

You also don't need the javascript to set the dropdownlist type. Just do this:

@Html.DropDownListFor(m => new Product().AccountTypeId, 
     new SelectList(Lookup.Instance.AccountTypes, 
         "AccountTypeId", "AccountTypeName"), "Select")

And make sure AccountTypeId is nullable int, and you put a [Required] attribute on it. The validator will make sure there's a value.

I'm also not sure why you're using the formSubmit code. image inputs are already submit types, so they submit the form when you click on them. You don't appear to actually be doing anything other than submitting the form again.

edited Feb 6, 2012 at 23:38

answered Feb 6, 2012 at 23:31

Erik Funkenbusch

93.7k29 gold badges201 silver badges292 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

JTennessen Over a year ago

Thanks for the tips -- as I'm sure you can tell, I'm very green at this, so I need all the pointers I can get! :-) On your first point, I know. Problem is, this view also contains existing Products (as I mentioned, I simplified this for posting -- maybe too much). Perhaps I should put the Product creation stuff in a partial view? Regarding AccountTypeId, the underlying db column is not nullable. Can I make the property nullable in that case?

JTennessen Over a year ago

The partial view approach worked like a charm -- thanks so much for pointing me in that direction! I didn't even end up having to make the AccountTypeId nullable. :-)

Collectives™ on Stack Overflow

Validating a drop down list in MVC3?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related