Saturday, December 26, 2009

Injecting Javasript into ASP.NET/MVC with a litlle help from ? Rich Stahl

An example of using JQuery with ASP.NET/MVC with Rick Stahl''s Web Utility.

Let's assume you want to use JQuery where you wish to have client side data sent back to a controller without a full page post back.

For the project:
You need to inject a client-side JavaScript. While you can spin one up by hand, why not use go green and recycle? Rich Stahl's site: has a variety of tools, some of which are free. Download What we're interested in here is the Web Utility Support Classes

Download the utility and add references for Westwind.Utilities and Westwind.Web to your project. You'll also need to add ScriptVariableInjectionHelper.cs to your helpers folder.

ScriptVariableInjectionHelper provides an easy way for server code to publish strings into client script code. This object basically provides a mechanism for adding key value pairs and embedding those values into an object that is hosted on the client.

For the Master Page:
Before you start injecting scripts willy-nilly all over your pages, it is better to inject all of your client-side scripts into the header along with your other JavaScript includes.. If you are using a master page, this becomes very easy. Beneath where you put all of your other site-wide include tags, and above a content placeholder for page-level scripts, I also add a simple test for controller scripts I inject into the ViewData and a test to verify it is there before you write it out.

<script type="text/javascript" language="javascript" src="<%=Url.Content(">"></script>
<% if(ViewData.Contains("clientScript")){
asp:contentplaceholder id="Scripts" runat="server">

For the Controller:
Now that we have a way to inject our script and a target to inject it into, we need to simply send it down for manipulation.

From your ActionMethod we add a call to a new InjectClientScript method...
public virtual ActionResult Edit(Guid id)

Criterion model = _CriterionSvc.GetCriterion(id);
return View(model);

private void InjectClientScript(object model)
// instantiate the utility (view is the name of the JavaScript object that will appear in the View
ScriptVariables scriptVars = new ScriptVariables("view");
// add our ProfileCommon data (user context)
scriptVars.Add("Profile", profile.Preferences);
// add our model being injected
if (model != null)
scriptVars.Add("Model", model);
// call the westwind utility and inject into viewdata
ViewData["clientScript"] = scriptVars.GetClientScript(true);

For the view:
The output is injected into a variable called view, which in turn contains our Controller objects we injected (Profile and Model). Note Model contains objects of its own. In this example, CriterionType is one such object. You can configure the westwind utility to traverse child objects or not.

You now simply need to access your javascript variables.Below is a simple example of accessing those variables and sending them to a jquery function that would populate a dropdown.

$.PopulateDropdown("CriterionTypeId", "/CriterionType/GetCriterionTypeCollection/" + view.Model.CriterionType.DomainId, view.Model.CriterionTypeId);

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