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POReturning a view with it's model from an ActionFilterAttribute
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  1. POReturning a view with it's model from an ActionFilterAttribute
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    copied!<p>When implementing error-handling using the built-in validation-helpers on a strongly-typed view, you usually create a try/catch block within the controller and return a view with it's corresponding model as a parameter to the <code>View()</code> method: <br /><br /><br /> <strong>The controller</strong></p> <pre><code>public class MessageController : Controller { [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(Models.Entities.Message message) { try { // Insert model into database var dc = new DataContext(); dc.Messages.InsertOnSubmit(message); dc.SubmitChanges(); return RedirectToAction("List"); } catch { /* If insert fails, return a view with it's corresponding model to enable validation helpers */ return View(message); } } } </code></pre> <p><br /><br /> <strong>The view</strong></p> <pre><code>&lt;%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage&lt;Models.Entities.Message&gt;" %&gt; &lt;%= Html.ValidationSummary("Fill out fields marked with *") %&gt; &lt;% using (Html.BeginForm()) { %&gt; &lt;div&gt;&lt;%= Html.TextBox("MessageText") %&gt;&lt;/div&gt; &lt;div&gt;&lt;%= Html.ValidationMessage("MessageText", "*") %&gt;&lt;/div&gt; &lt;% } %&gt; </code></pre> <p><br /><br /> I've implemented a simple error-handler in the form of an ActionFilterAttribute, which will be able to either redirect to a generic error view, or redirect to the view which threw an exception, and let the validation-helpers spring to life.</p> <p>Here's how my ActionFilterAttribute looks:</p> <pre><code>public class ErrorLoggingAttribute : ActionFilterAttribute, IExceptionFilter { private Boolean _onErrorRedirectToGenericErrorView; /// &lt;param name="onErrorRedirectToGenericErrorView"&gt; /// True: redirect to a generic error view. /// False: redirect back the view which threw an exception /// &lt;/param&gt; public ErrorLoggingAttribute(Boolean onErrorRedirectToGenericErrorView) { _onErrorRedirectToGenericErrorView = onErrorRedirectToGenericErrorView; } public void OnException(ExceptionContext ec) { if (_onErrorRedirectToGenericErrorView) { /* Redirect back to the view where the exception was thrown and include it's model so the validation helpers will work */ } else { // Redirect to a generic error view ec.Result = new RedirectToRouteResult(new RouteValueDictionary { {"controller", "Error"}, {"action", "Index"} }); ec.ExceptionHandled = true; } } } </code></pre> <p>Redirecting to the view which threw the exception is fairly simple. But here's the kicker: In order for the validation helpers to work, you need to provide the view with it's model.</p> <p>How would you return the view which threw an exception and provide the view with it's corresponding model? (In this case <code>Models.Entities.Message</code>).</p>
 

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