We’ve got ourselves a page which acts as a component and shows some stocks. Now lets put a link in that component view to show a specific stock, and lets say we want to call that using ajax (I’m using jQuery for my examples)

$("#stockDiv").load('/StockComponentController/DisplaySymbol');

We won’t get very far here because the ComponentController can’t accept a call to it in this fashion, therefore calling back to our component in any fashion other than a Html.RenderComponent call won’t work. I also don’t like this behavior because we have to use aspx pages with ComponentControllers, it just feels more appropriate to use an ascx. Also if we use a regular Controller we can do what was posted above much more easily. We can through ajax refresh the UserControl by using the default action behavior. This works quite well. for example:

$(document).ready(function(){
var symbol= "sym=" + $("#txtSymbol").get(0).value;
$("#stockDiv").load('/User/GetSymbol/' + symbol); });

UserControls actually work rather well except for the initial page load. We’re forced to pass them ViewData from the ViewPage, whereas ComponentControllers work well for the page load but fall apart if we want to interact with them. With that in mind I’ve “frankensteined” together the missing piece. What could work really well is a RenderControl helper which acts more like the RenderComponent, but allows us to render anything which derives from a controller. With this we can write an action which renders to a ViewUserControl and place that nicely right where we like it:

public static string RenderControl<TController>(this HtmlHelper helper, Expression<Action<TController>> action) where TController : Controller, new()
{

TController local = Activator.CreateInstance<TController>();
local.ControllerContext = helper.ViewContext;
MethodCallExpression body = action.Body as MethodCallExpression;
string name = body.Method.Name;
MethodInfo method = local.GetType().GetMethod(name);
List<object> list = new List<object>();
foreach (Expression exp in body.Arguments)
{

ConstantExpression exp1 = (ConstantExpression)exp;
object item = exp1.Value;
list.Add(item);

}
ActionResult result = (ActionResult)method.Invoke(local, list.ToArray());
result.ExecuteResult(local.ControllerContext);
return string.Empty;
}

There are a few caveats that I’m not particularly thrilled with and haven’t had the chance to refine as of yet. I took the RenderComponent helper and translated it to work for a Controller. As you can tell the return is the sticky part. The html helper expects a string return, but the ExecuteResult method uses the ViewEngine to output its html. With that behavior we’ve already output out html by the result.Execute…. line, but if we set the return value to void, it throws off the HtmlHelper behavior. I’m pretty sure that can be ammended.

Now we can write:

<%=Html.RenderControl<StockController>(c => c.ShowRecentStocks()) %>

This gives us all the benefits of using ViewUserControls and Controllers which I find superior to ComponentControllers and ViewPages. It feels counterintuitive to put ViewPages inside ViewPages and avoiding it while still getting the ability to have actions which partially render pages is excellent. I have not tested this for every situation but I do believe it should work as needed.

Jeremy