Why won't my Edit screen validation allow null?

Question

I added a field to a view model for a Document that should allow the user to associate it with a Tenant. It works fine if the user does assign a tenant, but if they select the null option from the dropdown, then the validation tells me that "The ItemID field is required.", where ItemID is a field on TenantViewModel.

It occurs to me that perhaps I'm using editor templates wrong - I'm trying to select from a list of tenants, not edit a tenant. If that's wrong, let me know, and maybe suggest a better way to get the dropdown.

namespace TenantPortal.Models
{
    public class DocumentViewModel
    {
        ...

        [UIHint("SelectTenant")]
        public TenantViewModel Tenant { get; set; }
     }

    public class TenantViewModel
    {
        private Tenant _ten = null;

        public int ItemID { get; set; }

        public string Display_Name { get; set; }

        public string Legal_Name { get; set; }

        ...
    }
}

Editor Template: SelectTenant.cshtml

@using CMS.DocumentEngine.Types.Tenantportal
@using TenantPortal.Models
@model TenantViewModel

@{ 
    Layout = null;

    var opts = new SelectList(TenantProvider.GetTenants(), "ItemID", "Display_Name");
}

@Html.DropDownListFor(model => model.ItemID, opts, "(none)")

Derviş Kayımbaşıoğlu · Accepted Answer · 2019-02-07 17:56:02Z

1

If you use data annotations you can add validation to your model.

See my example below:

public class TenantViewModel
{
    private Tenant _ten = null;

    [Required]
    public int ItemID { get; set; }

    [Required]
    [MaxLength(30)]
    public string Display_Name { get; set; }

    public string Legal_Name { get; set; }

    ...
}

For further information about data annotations check this

Also, on your code/controller-action side, you need to use ModelState.IsValid check in order to verify whether your model is valid or not

answered Feb 7, 2019 at 17:56

Derviş Kayımbaşıoğlu

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Comments

David · Accepted Answer · 2019-02-07 18:00:11Z

1

Your ItemID field is an int so it does not allow null values so the model validation fails. Try changing it to int? (a nullable int). If a value is not set in the form, then the value will be null, but if a value is selected, the ItemID will be the selected value.

answered Feb 7, 2019 at 18:00

David

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1 Comment

user1269310 Over a year ago

I don't want to change any of the Tenant fields with this editor, just select between tenants. I would think setting the Tenant field on DocumentViewModel to a nullable type would make sense, except it's already nullable.

user1269310 · Accepted Answer · 2019-02-07 18:56:13Z

0

I ended up adding another property to my document view model named TenantID, having it communicate with the Tenant property behind-the-scenes, and creating SelectLists for TenantID dropdowns on both Create and Edit views. It's less elegant than I would like, but it works.

answered Feb 7, 2019 at 18:56

user1269310

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