Rendering a view to a string in MVC, then redirecting — workarounds?

Question

I can\'t render a view to a string and then redirect, despite this answer from Feb (after version 1.0, I think) that claims it\'s possible. I thought I was doing something w

Answer 1

public Action SendEmail(int id)
{
  //Let's say that id is the db id of an order that a customer has just placed.

  //Go get that model from the db.
  MyModel model = new Model(id);

  //Now send that email. Don't forget the model and controller context.
  SendEmail(model, this.ControllerContext);

  //Render (or redirect!)
  return RedirectToAction("Wherever");
}

private static void SendEmail(MyModel model, ControllerContext controllerContext)
{
  //Recreate the viewdata
  ViewDataDictionary viewData = controllerContext.Controller.ViewData;
  viewData["Order"] = model;
  string renderedView = "";
  CustomRenderers customRenderers = new CustomRenderers();

  //Now render the view to string
  //ControllerContext, ViewPath, MasterPath, ViewDataDictionary, TempDataDictionary
  //As you can see, we're not passing a master page, and the tempdata is in this instance.
  renderedView = RenderViewToString(controllerContext, "~/Views/Orders/Email.aspx", "", viewData, null);

  //Now send your email with the string as the body.
  //Not writing that, as the purpose is just to show the rendering. :)
}


//Elsewhere...
public class CustomRenderers
{
  public virtual string RenderViewToString(ControllerContext controllerContext, string viewPath, string masterPath, ViewDataDictionary viewData, TempDataDictionary tempData)
  {
    if (tempData == null)
    {
    tempData = new TempDataDictionary();
    }

    Stream filter = null;
    ViewPage viewPage = new ViewPage();

    //Right, create our view
    viewPage.ViewContext = new ViewContext(controllerContext, new WebFormView(viewPath, masterPath), viewData, tempData);

    //Get the response context, flush it and get the response filter.
    var response = viewPage.ViewContext.HttpContext.Response;
    response.Flush();
    var oldFilter = response.Filter;

    try
    {
    //Put a new filter into the response
    filter = new MemoryStream();
    response.Filter = filter;

    //Now render the view into the memorystream and flush the response
    viewPage.ViewContext.View.Render(viewPage.ViewContext, viewPage.ViewContext.HttpContext.Response.Output);
    response.Flush();

    //Now read the rendered view.
    filter.Position = 0;
    var reader = new StreamReader(filter, response.ContentEncoding);
    return reader.ReadToEnd();
    }
    finally
    {
    //Clean up.
    if (filter != null)
    {
      filter.Dispose();
    }

    //Now replace the response filter
    response.Filter = oldFilter;
    }
  }
}

In your Orders/Email.aspx view, make sure you refer to everything from the ViewData, rather than the model. you can do this:

<% MyModel model = (MyModel)ViewData["Order"] %>

Answer 2

Updated.

Now that I understand that you want to use the view engine to generate the actual email in html, I propose the following:

Code to render action to text within a controller: http://mikehadlow.blogspot.com/2008/06/mvc-framework-capturing-output-of-view_05.html

Minor edits to your code:

public ActionResult Certifications(string email_intro)
{
     //a lot of stuff              
     ViewData["users"] = users;              
     if (isPost())             
     {                 
         //create the viewmodel                 
         var view_model = new ViewModels.Emails.Certifications.Open(userContext) { emailIntro = email_intro };                  

         foreach (var user in users)                 
         {                     
             if (user.Email_Address.IsValidEmailAddress())                     
             {                         
                 view_model.user = user;                         
                 view_model.certification302Summary.subProcessesOwner = new SubProcess_Certifications(RecordUpdating.Role.Owner, null, null, user.User_ID, repository);                         

                 SendEmail(view_model);                     
             }                 
         }                  
         return RedirectToAction("Certifications");             
     }              
     return View();         
 } 

 public void SendEmail(ViewModels.Emails.Certifications.Open model)         
 {             
    var vd = context.Controller.ViewData;             
    vd["model"] = model;             
    var renderer = new CustomRenderers();             

    // Implement the actual email rendering as a regular action method on this controller
    var text = this.CaptureActionHtml(c => (ViewResult)c.RenderEmail(model));

    var a = text;         
} 

Answer 3

Here is an alternative method for rendering a view to a string that never results in data being output to the response (therefore it should avoid your problem): http://craftycodeblog.com/2010/05/15/asp-net-mvc-render-partial-view-to-string/

To render a regular view instead of a partial view, you'll need to change "ViewEngines.Engines.FindPartialView" to "ViewEngines.Engines.FindView".