ASP.net MVC: Getting a Partial View's HTML from inside of the controller

Question

I have developed a simple mechanism for my mvc website to pull in html via jquery which then populates a specified div. All is well and it looks cool.
My problem is that i'm now creating html markup inside of my controller (Which is very easy to do in VB.net btw) I'd rather not mix up the sepparation of concerns.

Is it possible to use a custom 'MVC View User Control' to suit this need? Can I create an instance of a control, pass in the model data and render to html? It would then be a simple matter of rendering and passing back to the calling browser.

Answer 1

In rails this is called rendering a partial view, and you do it with render :partial => 'yourfilename'. I believe ASP.NET MVC has a similar RenderPartial method, but I can't find the official docs for MVC to confirm or deny such a thing.

Answer 2

After much digging in google i have found the answer. You can not get easy access to the html outputted by the view.

http://ayende.com/Blog/archive/2008/11/11/another-asp.net-mvc-bug-rendering-views-to-different-output-source.aspx

Answer 3

You would create your action like this:

        public PartialViewResult LoginForm()
        {
            var model = // get model data from somewhere
            return PartialView(model);
        }

And the action would return the rendered partial view to your jquery response.

Your jquery could look something like this:

$('#targetdiv').load('/MyController/LoginForm',function(){alert('complete!');});

Answer 4

You should use jquery to populate your divs (and create new html elements if needed), and Json serialization for ActionResult.

Other way is to use jquery to call some controller/action, but instead json use regular View (aspx or ascx, webforms view engine) for rendering content, and with jquery just inject that html to some div. This is half way to UpdatePanels from asp.net ajax...

I would probably go with first method, with json, where you have little more job to do, but it's much more "optimized", because you don't transfer whole html over the wire, there are just serialized objects. It's the way that "big ones" (gmail, g docs, hotmail,..) do it - lot of JS code that manipulates with UI.

If you don't need ajax, then you basically have two ways of calling partial views:

• html.renderpartial("name of ascx")
• html.RenderAction(x=>x.ActionName) from Microsoft.web.mvc (mvc futures)

Answer 5

Hey Everyone,

I put together a rough framework which allows you to render views to a string from a controller method in MVC Beta. This should help solve this limitation for now.

Additionally, I also put together a Rails-like RJS javascript generating framework for MVC Beta.

Check it out at http://www.brightmix.com/blog/how-to-renderpartial-to-string-in-asp-net-mvc and let me know what you think.

Answer 6

You have several options.

Create a MVC View User Control and action handler in your controller for the view. To render the view use

<% Html.RenderPartial("MyControl") %>

In this case your action handler will need to pass the model data to the view

public ActionResult MyControl ()
{
    // get modelData

    render View (modelData);
}

Your other option is to pass the model data from the parent page. In this case you do not need an action handler and the model type is the same as the parent:

<% Html.RenderPartial("MyControl", ViewData.Model) %>

If your user control has it's own data type you can also construct it within the page

In MyControl.ascx.cs:

public class MyControlViewData
{
    public string Name { get; set; }
    public string Email { get; set; }
}

public partial class MyControl : System.Web.Mvc.ViewUserControl <MyControlViewData>
{
}

And in your page you can initialize your control's data model:

<% Html.RenderPartial("MyControl", new MyControlViewData ()
   {
        Name= ViewData.Model.FirstName,
        Email = ViewData.Model.Email,
   });
 %>

Answer 7

This is a solution that is working with ASP.Net MVC 1.0 (many that claim to work with beta 3 don't work with 1.0), doesn't suffer of the 'Server cannot set content type after HTTP headers have been sent' problem and can be called from within a controller (not only a view):

/// <summary>
/// Render a view into a string. It's a hack, it may fail badly.
/// </summary>
/// <param name="name">Name of the view, that is, its path.</param>
/// <param name="data">Data to pass to the view, a model or something like that.</param>
/// <returns>A string with the (HTML of) view.</returns>
public static string RenderPartialToString(string controlName, object viewData) {
    ViewPage viewPage = new ViewPage() { ViewContext = new ViewContext() };
    viewPage.Url = GetBogusUrlHelper();

    viewPage.ViewData = new ViewDataDictionary(viewData);
    viewPage.Controls.Add(viewPage.LoadControl(controlName));

    StringBuilder sb = new StringBuilder();
    using (StringWriter sw = new StringWriter(sb)) {
        using (HtmlTextWriter tw = new HtmlTextWriter(sw)) {
            viewPage.RenderControl(tw);
        }
    }

    return sb.ToString();
}

public static UrlHelper GetBogusUrlHelper() {
  var httpContext = HttpContext.Current;

  if (httpContext == null) {
    var request = new HttpRequest("/", Config.Url.ToString(), "");
    var response = new HttpResponse(new StringWriter());
    httpContext = new HttpContext(request, response);
  }

  var httpContextBase = new HttpContextWrapper(httpContext);
  var routeData = new RouteData();
  var requestContext = new RequestContext(httpContextBase, routeData);

  return new UrlHelper(requestContext);
}

It's a static method you can drop somewhere you find it convenient. You can call it this way:

string view = RenderPartialToString("~/Views/Controller/AView.ascx", someModelObject); 

Answer 8

This post will solve your problem without the need to create fake UrlHelpers and such: http://craftycodeblog.com/2010/05/15/asp-net-mvc-render-partial-view-to-string/

Answer 9

I've done something similar for an app I'm working on. I have partial views returning rendered content can be called using their REST path or using:

<% Html.RenderAction("Action", "Controller"); %>

Then in my actual display HTML I have a DIV which is filled from jQuery:

<div class="onload">/controller/action</div>

The jQuery looks like this:

<script type="text/javascript">
    $.ajaxSetup({ cache: false });

    $(document).ready(function () {
        $('div.onload').each(function () {
            var source = $(this).html();
            if (source != "") {
                $(this).load(source);
            }
        });
    });
</script>

This scans for all DIV that match the "onload" class and reads the REST path from their content. It then does a jQuery.load on that REST path and populates the DIV with the result.

Sorry gotta go catch my ride home. Let me know if you want me to elaborate more.