modelstate.isvalid not getting all the errors - asp.net-mvc

Question

I have this model :
[Required(ErrorMessage = "Please provide a valid EmailAddress")]
[EmailAddress]
[Display(Name = "Email")]
public string Email { get; set; }
[Required(ErrorMessage = "Please provide a company name")]
[Display(Name = "Company")]
public string CompanyName { get; set; }
[Required(ErrorMessage = "Please provide a username")]
[Display(Name = "Username")]
public string UserName { get; set; }
[Required(ErrorMessage = "Please select at least one language")]
public int[] SelectedLanguages { get; set; }
[Required(ErrorMessage = "Please select at least one business unit")]
public int[] SelectedBusinessUnits { get; set; }
Now when I do a post from my form using this model and I don't provide any of the values, I only get errormessages for Email, Company and UserName.
I don't get messages for the SelectedLanguages or the SelectedBusinessUnits.
What am i doing wrong?
THis is the view
#using (Html.BeginForm("Register", "Account", FormMethod.Post, new { #class = "form-horizontal", role = "form" }))
{
#Html.AntiForgeryToken()
<h4>Create a new account.</h4>
<hr />
#Html.ValidationSummary("", new { #class = "text-danger" })
<div class="form-group">
#Html.LabelFor(m => m.CompanyName, new { #class = "col-md-2 control-label" })
<div class="col-md-10">
#Html.TextBoxFor(m => m.CompanyName, new { #class = "form-control" })
</div>
</div>
<div class="form-group">
#Html.LabelFor(m => m.UserName, new { #class = "col-md-2 control-label" })
<div class="col-md-10">
#Html.TextBoxFor(m => m.UserName, new { #class = "form-control" })
</div>
</div>
<div class="form-group">
#Html.LabelFor(m => m.Email, new { #class = "col-md-2 control-label" })
<div class="col-md-10">
#Html.TextBoxFor(m => m.Email, new { #class = "form-control" })
</div>
</div>
<div class="form-group">
#foreach (var la in Model.Languages)
{
<input type="checkbox"
name="SelectedLanguages" value="#la.Id" id="#la.Id" />
<label for="#la">#la.Title</label>
}
</div>
<div class="form-group">
#foreach (var bu in Model.BusinessUnits)
{
<input type="checkbox"
name="SelectedBusinessUnits" value="#bu.Id" id="#bu.Id" />
<label for="#bu.Id">#bu.Title</label>
}
</div>
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" class="btn btn-default" value="Register" />
</div>
</div>
}

Answer 1

I think you have to go the way of writing a custom validation routine accompanied with a ValidationAttribute. Don't think a simple "out-of-the-box" validator exists for checking if one or more values are present in an array.
Check out this SO post to point you in the right direction.
Basic setup:
public class ArrayContainsValueAttribute: ValidationAttribute
{
// your checks here (pseudo)
if(!array.Any())
return false;
return true;
}
[ArrayContainsValue(ErrorMessage = "Please select at least one business unit")]
public int[] SelectedBusinessUnits { get; set; }