Html.Partial vs Html.RenderPartial & Html.Action v

Question

In ASP.NET MVC, what is the difference between:

• Html.Partial and Html.RenderPartial
• Html.Action and Html.RenderAction

Answer 1

Differences:

1. The return type of RenderPartial is void, where as Partial returns MvcHtmlString

2. Syntax for invoking Partial() and RenderPartial() methods in Razor views

   @Html.Partial("PartialViewName")
   @{ Html.RenderPartial("PartialViewName"); }

3. Syntax for invoking Partial() and RenderPartial() methods in webform views

[%: Html.Partial("PartialViewName") %]
[% Html.RenderPartial("PartialViewName"); %]

The following are the 2 common interview questions related to Partial() and RenderPartial() When would you use Partial() over RenderPartial() and vice versa?

The main difference is that RenderPartial() returns void and the output will be written directly to the output stream, where as the Partial() method returns MvcHtmlString, which can be assigned to a variable and manipulate it if required. So, when there is a need to assign the output to a variable for manipulating it, then use Partial(), else use RenderPartial().

Which one is better for performance?

From a performance perspective, rendering directly to the output stream is better. RenderPartial() does exactly the same thing and is better for performance over Partial().

Answer 2

@Html.Partial returns view in HTML-encoded string and use same view TextWriter object. @Html.RenderPartial this method return void. @Html.RenderPartial is faster than @Html.Partial

The syntax for PartialView:

 [HttpGet] 
 public ActionResult AnyActionMethod
 {
     return PartialView();
 }

Answer 3

Html.Partial: returns MvcHtmlString and slow

Html.RenderPartial: directly render/write on output stream and returns void and it's very fast in comparison to Html.Partial

Answer 4

More about the question:

"When Html.RenderPartial() is called with just the name of the partial view, ASP.NET MVC will pass to the partial view the same Model and ViewData dictionary objects used by the calling view template."

“NerdDinner” from Professional ASP.NET MVC 1.0

Answer 5

Think of @Html.Partial as HTML code copied into the parent page. Think of @Html.RenderPartial as an .ascx user control incorporated into the parent page. An .ascx user control has far more overhead.

'@Html.Partial' returns a html encoded string that gets constructed inline with the parent. It accesses the parent's model.

'@Html.RenderPartial' returns the equivalent of a .ascx user control. It gets its own copy of the page's ViewDataDictionary and changes made to the RenderPartial's ViewData do not effect the parent's ViewData.

Using reflection we find:

public static MvcHtmlString Partial(this HtmlHelper htmlHelper, string partialViewName, object model, ViewDataDictionary viewData)
{
    MvcHtmlString mvcHtmlString;
    using (StringWriter stringWriter = new StringWriter(CultureInfo.CurrentCulture))
    {
        htmlHelper.RenderPartialInternal(partialViewName, viewData, model, stringWriter, ViewEngines.Engines);
        mvcHtmlString = MvcHtmlString.Create(stringWriter.ToString());
    }
    return mvcHtmlString;
}

public static void RenderPartial(this HtmlHelper htmlHelper, string partialViewName)
{
    htmlHelper.RenderPartialInternal(partialViewName, htmlHelper.ViewData, null, htmlHelper.ViewContext.Writer, ViewEngines.Engines);
}

Answer 6

Here is what I have found:

Use RenderAction when you do not have a model to send to the view and have a lot of html to bring back that doesn't need to be stored in a variable.

Use Action when you do not have a model to send to the view and have a little bit of text to bring back that needs to be stored in a variable.

Use RenderPartial when you have a model to send to the view and there will be a lot of html that doesn't need to be stored in a variable.

Use Partial when you have a model to send to the view and there will be a little bit of text that needs to be stored in a variable.

RenderAction and RenderPartial are faster.