I have a list of objects that are organized in a tree using a Depth property:

public class Quota
{
    [Range(0, int.MaxValue, ErrorMessage = "Please enter an amount above zero.")]
    public int Amount { get; set; }

    public int Depth { get; set; }

    [Required]
    [RegularExpression("^[a-zA-Z]+$")]
    public string Origin { get; set; }

    // ... another properties with validation attributes
}

For data example (amount - origin)

100 originA
200 originB
    50 originC
    150 originD

the model data looks like:

IList<Quota> model = new List<Quota>();
model.Add(new Quota{ Amount = 100, Depth = 0, Origin = "originA");
model.Add(new Quota{ Amount = 200, Depth = 0, Origin = "originB");
model.Add(new Quota{ Amount = 50,  Depth = 1, Origin = "originC");
model.Add(new Quota{ Amount = 150, Depth = 1, Orinig = "originD");

Editing of the list

Then I use Editing a variable length list, ASP.NET MVC 2-style to raise editing of the list.

Controller actions QuotaController.cs:

public class QuotaController : Controller
{
    //
    // GET: /Quota/EditList
    public ActionResult EditList()
    {
        IList<Quota> model = // ... assigments as in example above;

        return View(viewModel);
    }

    //
    // POST: /Quota/EditList
    [HttpPost]
    public ActionResult EditList(IList<Quota> quotas)
    {
        if (ModelState.IsValid)
        {
            // ... save logic
            return RedirectToAction("Details");
        }
        return View(quotas); // Redisplay the form with errors
    }

    // ... other controller actions
}

View EditList.aspx:

<%@ Page Title="" Language="C#" ... Inherits="System.Web.Mvc.ViewPage<IList<Quota>>" %>

...
<h2>Edit Quotas</h2>
<%=Html.ValidationSummary("Fix errors:") %>
<% using (Html.BeginForm()) { 
     foreach (var quota in Model)
     {
         Html.RenderPartial("QuotaEditorRow", quota);
     } %>
<% } %>
...

Partial View QuotaEditorRow.ascx:

<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Quota>" %>

<div class="quotas" style="margin-left: <%=Model.Depth*45 %>px">
    <% using (Html.BeginCollectionItem("Quotas")) { %>
        <%=Html.HiddenFor(m=>m.Id) %>
        <%=Html.HiddenFor(m=>m.Depth) %>


        <%=Html.TextBoxFor(m=>m.Amount, new {@class = "number", size = 5})%>
        <%=Html.ValidationMessageFor(m=>m.Amount) %>

        Origin:
        <%=Html.TextBoxFor(m=>m.Origin)%>
        <%=Html.ValidationMessageFor(m=>m.Origin) %>

        ...
    <% } %>
</div>

Business rule validation

How do I implement validation of business rule: Amount of quota and sum of amounts of nested quotas should equal (e.a. 200 = 50 + 150 in example)?

I want to appropriate inputs Html.TextBoxFor(m=>m.Amount) be highlighted red if the rule is broken for it. In example if user enters not 200, but 201 - it should be red on submit.

Using sever validation only.

Thanks a lot for any advise.