How can I make the Required attribute for my custom DropDownList editor template operate client side?

Question

I have an editor template for DropDownLists that is marked with an attribute like this:

[AttributeUsage(AttributeTargets.Property)]
public class DropDownListAttribute : UIHintAttribute
{
    public string SelectListName { get; set; }
    public DropDownListAttribute(string selectListName)
        : base("DropDownList", "MVC", selectListName)
    {
        SelectListName = selectListName;
    }
}

And itself looks like this:

@using Comair.RI.UI.Core
@{
    var list = this.GetModelSelectList();
    var listWithSelected = new SelectList(list.Items, list.DataValueField, list.DataTextField, Model);
}
@Html.DropDownListFor(m => Model, listWithSelected, " - select - ")

My issue here is it only validates server side, which is very annoying for a user to resolve all client side validations, only to submit and get a new, surprise server side validation.

Answer 1

If your client side validation doesn't work it may be caused by one of the following reasons:

1. Your web.config doesn't have that enteries:

   &ltappSettings>
   <add key="ClientValidationEnabled" value="true" />
   <add key="UnobtrusiveJavaScriptEnabled" value="true" />
   </appSettings>
   

2. You forgotten to add validation scripts:

   <script src="@Url.Content("~/Scripts/jquery.validate.min.js")"></script>
   <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")"></script>
   

3. Your controls are not surrounded by Html.BeginForm or Ajax.BeginForm

4. Client-side validation can stop working in EditorFor after update to ASP.NET MVC 4 if you use:

   @Html.DropDownListFor(m => Model, listWithSelected, " - select - ")
   

   Replacing Model with m should resolve problem:

   @Html.DropDownListFor(m => m, listWithSelected, " - select - ")