the best way to maintain html snippets in ASP.NET MVC to return in ajax calls - ajax

Question

i'm looking for a best practices type answer here. basically i have a very chatty application which will be returning bits of data to the client very often. the bits of data returned eventually will end up being html added dynamically to the dom. so i'm trying to choose between the following 2 ways:
return just json data, create the html on the client side using jquery and possibly jquery templates
return the actual html that is build on the server side
i would like to make the choice that is most easily maintained. that is, i want the best way that will allow me to make updates to the html snippets very often.
i'm actually looking for a way to do #2 using ASP MVC partial views and want the ability to use string formatting. essentially i'm looking to make a call like this:
string sHtml = string.Format(GetNewTradeHtml(), "GOOG", "100", "635.50");
and I want GetNewTradeHtml() to actually get the html from a ASP MVC view instead of a string constant that might look like:
const string cNewTradeHtml = "<li><span>Symbol: {0}</span><span>Qty: {1}</span><span>Price: {2}</span></li>";
the string constants seems to be a popular way to do these kinds of things and i hate maintaining those...
basically i think i'm looking for a way to manage view several view templates that i can call ToString() on and get the raw html and use string formatting on it. and i'm hoping there is a suggested way to solve my particular problem natively in ASP MVC (without some hack). but perhaps (unfortunately) the string constants + string.format is the best way to maintain server side dynamic html...
UPDATE:
here's what i've learned since i've posted this question:
there are LOTS of posts here on SO about rendering a view into a string. a lot of different ways, some work with different versions of MVC some don't. some are cleaner than others, some are pretty heavy... ALL of which are normally some type of solution that require a controller context. so in most cases the solutions work great as responses to requests. but for my case, i need to do it outside of the context of a controller so now i need to either mock the controller or make a bunch of fake objects, neither of which i really want to deal with.
so i've determined that there is actually NO easy way to render a razor partial into its string representation without using a controller in a response. they really need to make an easy way to do this without mocking up controller context and request objects.

Answer 1

What are Views in asp.net mvc? They are just html templates, nothing more. They take model and replace template placeholders with model values. And indeed there's no more natural way to render html in asp.net mvc than using Views.
First, declare your view model
public class NewTradeViewModel
{
public string Symbol { get; set; }
public decimal Quantity { get; set; }
public decimal Price { get; set; }
}
than your controller action
public ViewResult GetNewTrade()
{
NewTradeViewModel model = new NewTradeViewModel;
model.Symbol = "GOOG";
model.Quantity = "100";
model.Price = 635.50m;
// PartialView, as you want just html snippets, not full layouts with master pages, etc
return PartialView("TemplateViewName", model);
}
and the very ordinary view - you may have any number of these, just change controller action to return specific one
#model NewTradeViewModel
<li><span>Symbol: #Model.Symbol</span><span>Qty: #Model.Quantity</span><span>Price: #Model.Price</span></li>

Answer 2

Since you mentioned that your app was "chatty" you should probably consider returning Json and rendering on the client side with a template engine.
This is really a toss up though because it looks like your snippets are pretty small.
If you do go with a sending JSON back and forth, I can recommend jquery templates or mustache
backbone.js can also help you better organize your client side components. It is pretty easy to get up and running with it. By default it works with jquery templates, but you can also plug in other templates if you like.
Here is a simple approach to storing templates in separate files, http://encosia.com/using-external-templates-with-jquery-templates/

Answer 3

ijjo,
Just looked at your question again and notice that you are referring to returning the html partialview as a string. there are loads of references here on SO to this type od function, but below is my version taken from an 'old' mvc app that's still in production. without further ado, it's an extension method that hooks into the controller:
public static class ExtensionMethods
{
public static string RenderPartialToString(this ControllerBase controller, string partialName, object model)
{
var vd = new ViewDataDictionary(controller.ViewData);
var vp = new ViewPage
{
ViewData = vd,
ViewContext = new ViewContext(),
Url = new UrlHelper(controller.ControllerContext.RequestContext)
};
ViewEngineResult result = ViewEngines
.Engines
.FindPartialView(controller.ControllerContext, partialName);
if (result.View == null)
{
throw new InvalidOperationException(
string.Format("The partial view '{0}' could not be found", partialName));
}
var partialPath = ((WebFormView)result.View).ViewPath;
vp.ViewData.Model = model;
Control control = vp.LoadControl(partialPath);
vp.Controls.Add(control);
var sb = new StringBuilder();
using (var sw = new StringWriter(sb))
{
using (var tw = new HtmlTextWriter(sw))
{
vp.RenderControl(tw);
}
}
return sb.ToString();
}
}
usage (as per archil's example above):
public ViewResult GetNewTrade()
{
NewTradeViewModel model = new NewTradeViewModel;
model.Symbol = "GOOG";
model.Quantity = "100";
model.Price = 635.50m;
// PartialView, as you want just html snippets, not full layouts with master pages, etc
return this.RenderPartialToString("TemplateViewName", model);
}
good luck and enjoy...