ASP.NET MVC partial views: input name prefixes

Suppose I have ViewModel like

public class AnotherViewModel
{
   public string Name { get; set; }
}
public class MyViewModel
{
   public string Name { get; set; }
   public AnotherViewModel Child { get; set; }
   public AnotherViewModel Child2 { get; set; }
}

In the view I can render a partial with

<% Html.RenderPartial("AnotherViewModelControl", Model.Child) %>

In the partial I'll do

<%= Html.TextBox("Name", Model.Name) %>
or
<%= Html.TextBoxFor(x => x.Name) %>

However, the problem is that both will render name="Name" while I need to have name="Child.Name" in order for model binder to work properly. Or, name="Child2.Name" when I render the second property using the same partial view.

How do I make my partial view automatically recognize the required prefix? I can pass it as a parameter but this is too inconvenient. This is even worse when I want for example to render it recursively. Is there a way to render partial views with a prefix, or, even better, with automatic reconition of the calling lambda expression so that

<% Html.RenderPartial("AnotherViewModelControl", Model.Child) %>

will automatically add correct "Child." prefix to the generated name/id strings?

I can accept any solution, including 3-rd party view engines and libraries - I actually use Spark View Engine (I "solve" the problem using its macros) and MvcContrib, but did not find a solution there. XForms, InputBuilder, MVC v2 - any tool/insight that provide this functionality will be great.

Currently I think about coding this myself but it seems like a waste of time, I can't believe this trivial stuff is not implemented already.

A lot of manual solutions may exists, and all of them are welcome. For example, I can force my partials to be based off IPartialViewModel<T> { public string Prefix; T Model; }. But I'd rather prefer some existing/approved solution.

UPDATE: there's a similar question with no answer here.

You can extend Html helper class by this :

using System.Web.Mvc.Html


 public static MvcHtmlString PartialFor<TModel, TProperty>(this HtmlHelper<TModel> helper, System.Linq.Expressions.Expression<Func<TModel, TProperty>> expression, string partialViewName)
    {
        string name = ExpressionHelper.GetExpressionText(expression);
        object model = ModelMetadata.FromLambdaExpression(expression, helper.ViewData).Model;
        var viewData = new ViewDataDictionary(helper.ViewData)
        {
            TemplateInfo = new System.Web.Mvc.TemplateInfo
            {
                HtmlFieldPrefix = name
            }
        };

        return helper.Partial(partialViewName, model, viewData);

    }

and simply use it in your views like this :

<%= Html.PartialFor(model => model.Child, "_AnotherViewModelControl") %>

and you will see everything is ok!

so far, i was searching for the same thing I have found this recent post:

http://davybrion.com/blog/2011/01/prefixing-input-elements-of-partial-views-with-asp-net-mvc/

<% Html.RenderPartial("AnotherViewModelControl", Model.Child, new ViewDataDictionary
{
    TemplateInfo = new System.Web.Mvc.TemplateInfo { HtmlFieldPrefix = "Child1" }
})
%>

My answer, based on the answer of Mahmoud Moravej including the comment of Ivan Zlatev.

    public static MvcHtmlString PartialFor<TModel, TProperty>(this HtmlHelper<TModel> helper, System.Linq.Expressions.Expression<Func<TModel, TProperty>> expression, string partialViewName)
    {
            string name = ExpressionHelper.GetExpressionText(expression);
            object model = ModelMetadata.FromLambdaExpression(expression, helper.ViewData).Model;
            StringBuilder htmlFieldPrefix = new StringBuilder();
            if (helper.ViewData.TemplateInfo.HtmlFieldPrefix != "")
            {
                htmlFieldPrefix.Append(helper.ViewData.TemplateInfo.HtmlFieldPrefix);
                htmlFieldPrefix.Append(name == "" ? "" : "." + name);
            }
            else
                htmlFieldPrefix.Append(name);
            
            var viewData = new ViewDataDictionary(helper.ViewData)
            {
                TemplateInfo = new System.Web.Mvc.TemplateInfo
                {
                    HtmlFieldPrefix = htmlFieldPrefix.ToString()
                }
            };

        return helper.Partial(partialViewName, model, viewData);
    }

Edit: The Mohamoud's answer is incorrect for nested partial rendering. You need to append the new prefix to the old prefix, only if it is necessary. This was not clear in the latest answers (:

Using MVC2 you can achieve this.

Here is the strongly typed view:

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<MvcLearner.Models.Person>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
	Create
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <h2>Create</h2>

    <% using (Html.BeginForm()) { %>
        <%= Html.LabelFor(person => person.Name) %><br />
        <%= Html.EditorFor(person => person.Name) %><br />
        <%= Html.LabelFor(person => person.Age) %><br />
        <%= Html.EditorFor(person => person.Age) %><br />
        <% foreach (String FavoriteFoods in Model.FavoriteFoods) { %>
            <%= Html.LabelFor(food => FavoriteFoods) %><br />
            <%= Html.EditorFor(food => FavoriteFoods)%><br />
        <% } %>
        <%= Html.EditorFor(person => person.Birthday, "TwoPart") %>
        <input type="submit" value="Submit" />
    <% } %>
    
</asp:Content>

Here is the strongly typed view for the child class (which must be stored in a subfolder of the view directory called EditorTemplates):

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

<%= Html.LabelFor(birthday => birthday.Day) %><br />
<%= Html.EditorFor(birthday => birthday.Day) %><br />

<%= Html.LabelFor(birthday => birthday.Month) %><br />
<%= Html.EditorFor(birthday => birthday.Month) %><br />

Here is the controller:

public class PersonController : Controller
{
    //
    // GET: /Person/
    [AcceptVerbs(HttpVerbs.Get)]
    public ActionResult Index()
    {
        return View();
    }

    [AcceptVerbs(HttpVerbs.Get)]
    public ActionResult Create()
    {
        Person person = new Person();
        person.FavoriteFoods.Add("Sushi");
        return View(person);
    }

    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Create(Person person)
    {
        return View(person);
    }
}

Here are the custom classes:

public class Person
{
    public String Name { get; set; }
    public Int32 Age { get; set; }
    public List<String> FavoriteFoods { get; set; }
    public TwoPart Birthday { get; set; }

    public Person()
    {
        this.FavoriteFoods = new List<String>();
        this.Birthday = new TwoPart();
    }
}

public class TwoPart
{
    public Int32 Day { get; set; }
    public Int32 Month { get; set; }
}

And the output source:

<form action="/Person/Create" method="post"><label for="Name">Name</label><br /> 
    <input class="text-box single-line" id="Name" name="Name" type="text" value="" /><br /> 
    <label for="Age">Age</label><br /> 
    <input class="text-box single-line" id="Age" name="Age" type="text" value="0" /><br /> 
    <label for="FavoriteFoods">FavoriteFoods</label><br /> 
    <input class="text-box single-line" id="FavoriteFoods" name="FavoriteFoods" type="text" value="Sushi" /><br /> 
    <label for="Birthday_Day">Day</label><br /> 
    <input class="text-box single-line" id="Birthday_Day" name="Birthday.Day" type="text" value="0" /><br /> 
 
    <label for="Birthday_Month">Month</label><br /> 
    <input class="text-box single-line" id="Birthday_Month" name="Birthday.Month" type="text" value="0" /><br /> 
    <input type="submit" value="Submit" /> 
</form>

Now this is complete. Set a breakpoint in the Create Post controller action to verify. Don't use this with lists however because it wont work. See my question on using EditorTemplates with IEnumerable for more on that.

This is an old question, but for anyone arriving here looking for a solution, consider using EditorFor, as suggested in a comment in https://stackoverflow.com/a/29809907/456456. To move from a partial view to an editor template, follow these steps.

1. Verify that your partial view is bound to ComplexType.

2. Move your partial view to a subfolder EditorTemplates of the current view folder, or to the folder Shared. Now, it is an editor template.

3. Change @Html.Partial("_PartialViewName", Model.ComplexType) to @Html.EditorFor(m => m.ComplexType, "_EditorTemplateName"). The editor template is optional if it's the only template for the complex type.

Html Input elements will automatically be named ComplexType.Fieldname.

PartailFor for asp.net Core 2 in case someone needs it.

    public static ModelExplorer GetModelExplorer<TModel, TResult>(this IHtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TResult>> expression)
    {
        if (expression == null)
            throw new ArgumentNullException(nameof(expression));
        return ExpressionMetadataProvider.FromLambdaExpression(expression, htmlHelper.ViewData, htmlHelper.MetadataProvider);
    }

    public static IHtmlContent PartialFor<TModel, TResult>(this IHtmlHelper<TModel> helper, Expression<Func<TModel, TResult>> expression, string partialViewName, string prefix = "")
    {
        var modelExplorer = helper.GetModelExplorer(expression);
        var viewData = new ViewDataDictionary(helper.ViewData);
        viewData.TemplateInfo.HtmlFieldPrefix += prefix;
        return helper.Partial(partialViewName, modelExplorer.Model, viewData);
    }

I came across this issue also and after much pain i found it was easier to redesign my interfaces such that i didn't need to post back nested model objects. This forced me to change my interface workflows: sure i now require the user to do in two steps what i dreamed of doing on one, but the usability and code maintainability of the new approach is of greater value to me now.

Hope this helps some.

As stated here: https://stackoverflow.com/a/58943378/3901618 - for ASP.NET Core - you can use the partial tag helper.

<partial name="AnotherViewModelControl" for="Child" />
<partial name="AnotherViewModelControl" for="Child2" />

It generates all required name prefixes.

You could add a helper for the RenderPartial which takes the prefix and pops it in the ViewData.

    public static void RenderPartial(this HtmlHelper helper,string partialViewName, object model, string prefix)
    {
        helper.ViewData["__prefix"] = prefix;
        helper.RenderPartial(partialViewName, model);
    }

Then a further helper which concatenates the ViewData value

    public static void GetName(this HtmlHelper helper, string name)
    {
        return string.Concat(helper.ViewData["__prefix"], name);
    }

and so in the view ...

<% Html.RenderPartial("AnotherViewModelControl", Model.Child, "Child.") %>

in the partial ...

<%= Html.TextBox(Html.GetName("Name"), Model.Name) %>

Like you, I add Prefix property (a string) to my ViewModels which I append before my model bound input names. (YAGNI preventing the below)

A more elegant solution might be a base view model that has this property and some HtmlHelpers that check if the view model derives from this base and if so append the prefix to the input name.

Hope that helps,

Dan

How about just before you call RenderPartial you do

<% ViewData["Prefix"] = "Child."; %>
<% Html.RenderPartial("AnotherViewModelControl", Model.Child) %>

Then in your partial you have

<%= Html.TextBox(ViewData["Prefix"] + "Name", Model.Name) %>