How to post each submodel alone with validation into consideration? - asp.net-mvc

Question

I have a view which is bound with a ViewModel which contains multiple viewmodels.
Now, the parent view contains views(rendered by #html.partial) each view bound with its corresponding viewmodel and has its own form action.
My Question:
I could view the data correctly, but i can't submit each subview alone, so how can post each submodel alone?
Also, when there would be modelstate errors how can i refer to the correct subview?
Any idea would be appreciated.
Extra info:
The code sample shows what i did exactly:
ViewModel:
public class ViewModelParent
{
public ViewModelChild1 ViewModelC1 {get; set;}
public ViewModelChild2 ViewModelC2 {get; set;}
public ViewModelChild3 ViewModelC3 {get; set;}
}
Controller:
public ActionResult GetParent()
{
return view(new ViewModelParent());
}
Views:
GetParent.cshtml (contains views for each submodel).
#model Models.ViewModelParent
#Html.Partial("~/Views/Children/GetC1.cshtml", Model.ViewModelC1)
#Html.Partial("~/Views/Children/GetC2.cshtml", Model.ViewModelC2)
#Html.Partial("~/Views/Children/GetC3.cshtml", Model.ViewModelC3)
Children views:
GetC1.cshtml
#model ViewModelChild1
<form action="#Url.Action("GetC1", "Child"" method="POST" class="smart-form" id="frm_child1">
#Html.AntiForgeryToken()
#Html.ValidationSummary()
#* controls here*#
</form>
The same applies for the rest children views GetC2.cshtml & GetC3.cshtml

Answer 1

I've done something similar in the past.
I'd recommend this as a possible approach (assuming you want to stick with full page postbacks instead of going the ajax route).
Use your existing Parent ViewModel class (with child Models)
public class ViewModelParent
{
public ViewModelChild1 ViewModelC1 {get; set;}
public ViewModelChild2 ViewModelC2 {get; set;}
public ViewModelChild3 ViewModelC3 {get; set;}
}
Have the partial views each use the Parent Model
#model Models.ViewModelParent
#Html.Partial("~/Views/Children/GetC1.cshtml", Model)
#Html.Partial("~/Views/Children/GetC2.cshtml", Model)
#Html.Partial("~/Views/Children/GetC3.cshtml", Model)
The Child views each have the parent Model, but only contain form elements for the Child Model of that view. If you want a validation summary in every partial view you have to get a bit creative - I'll explain later...
eg: GetC1.cshtml
#model ViewModelParent
#using(Html.BeginForm("GetParent", "ParentControllerName", null, FormMethod.Post, new {#class="smart-form" id="frm_child1"}))
{
#Html.AntiForgeryToken()
#Html.ValidationSummaryForGroup(ViewBag.ChildType, "Child1") #* I'll explain this later *#
#* controls here - eg... *#
#Html.TextBoxFor(m => m.ViewModelChild1.Property1)
}
Then your controller can simply farm out the child methods if the form is valid (or return if not)
Eg:
public class ParentControllerNameController : Controller
{
public ActionResult GetParent()
{
return View(new ViewModelParent());
}
[HttpPost]
public ActionResult GetParent(ViewModelParent model)
{
if (ModelState.IsValid)
{
if (model.ViewModelC1 != null)
{
return GetC1(model.ViewModelC1);
}
else if (model.ViewModelC2 != null)
{
return GetC2(model.ViewModelC2)
}
else if (model.ViewModelC3 != null)
{
return GetC3(model.ViewModelC3)
}
} else {
// invalid!
if (model.ViewModelC1 != null)
{
ViewBag.ChildType = "Child1";
}
else if (model.ViewModelC2 != null)
{
ViewBag.ChildType = "Child2";
}
else if (model.ViewModelC3 != null)
{
ViewBag.ChildType = "Child3";
}
// needed to prevent null reference errors
if (model.ViewModelC1 == null) model.ViewModelC1 = new ViewModelChild1();
if (model.ViewModelC2 == null) model.ViewModelC2 = new ViewModelChild2();
if (model.ViewModelC3 == null) model.ViewModelC3 = new ViewModelChild3();
}
return View(model);
}
}
The above else-if statements will work, because each child view only contains properties for that child model - hence the other child viewmodels are null.
Note I used a new Html Helper extension above that I created that wraps the Validation Summary so you can display errors specific to the child model. A simple display/not display is insufficient because you'd lose client side validation errors being shown otherwise.
Of course this is only necessary when you have a validation summary in every partial view. If there's just one validation summary then you can stick with a simple #Html.ValidationSummary()
namespace System.Web.Mvc.Html
{
public static class ValidationSummaryForGroupExtensions
{
public static MvcHtmlString ValidationSummaryForGroup(this HtmlHelper html, string testValue, string expectedValue)
{
return ValidationSummaryForGroup(html, testValue, expectedValue, false);
}
/// <summary>
/// Displays a validation summary which shows serverside errors only if the specified testvalue and value are equal. Client side validation will work as normal.
/// <para>The purpose of this is to allow multiple valiation summaries (for multiple forms) on a single page.</para>
/// </summary>
/// <param name="testValue">Value to test (could be a value in viewbag)</param>
/// <param name="expectedValue">Value to expect if the server side errors are to be displayed.</param>
/// <returns></returns>
public static MvcHtmlString ValidationSummaryForGroup(this HtmlHelper html, string testValue, string expectedValue, bool excludePropertyErrors)
{
if (testValue != null && testValue.ToLower() == expectedValue.ToLower())
return html.ValidationSummary(excludePropertyErrors);
return new MvcHtmlString("<div class=\"validation-summary-valid\" data-valmsg-summary=\"true\"><ul><li style=\"display:none\"></li></ul></div>");
}
}
}
Of course you could do partial postbacks using ajax - in which case the child views could be directly for the child models, and each child form postback directly to the relevant method in your controller.

Answer 2

This is simple, in the handler of the post method of the controller, call the name of the parameter after the property name in the view model.
So in you view model you have:
public class ViewModelParent
{
public ViewModelChild1 viewModelC1 {get; set;}
public ViewModelChild2 viewModelC2 {get; set;}
public ViewModelChild3 viewModelC3 {get; set;}
}
In the post handler of your controller you will need something like:
<HttpPost()>
Function GetC1(viewModelC1 As ViewModelChild1 ) As ActionResult
in the html all the properties will be names like 'viewModelC1.nameofsomething' and this helps the model binder map the properties up. The above is VB.net but you should get the idea.
hope that helps
Andy