Question

I have a form on a webpage that I submit using the jquery form plugin. This form includes a file upload option. The MVC3 action that I post to returns JSON. Since the plugin falls back to using an iframe on older browsers you need to wrap your JSON with a

<textarea>JSON data...</textarea>

I tried changing the return type of the action to string and just appending the text area tags the the JSON object.ToString() but no go. How can I wrap my JSON result in a textarea when !Request.IsAjaxRequest()

Here is an example of me just trying to return the JSON as a string (which doesn’t work)

[HttpPost]
    public string CreateEntry(EntryCreateViewModel model)
    {
        if (!ModelState.IsValid)
        {
            return WrapInTextArea(!Request.IsAjaxRequest(), Json(new object[] { false, 0, this.RenderPartialViewToString("_EntryCreateFormPartial", model) }).ToString());
        }

This works in modern browsers but I suspect (based on the docs) will fail in older browsers that use an iframe

[HttpPost]
    public ActionResult CreateEntry(EntryCreateViewModel model)
    {
        if (!ModelState.IsValid)
        {
            return Json(new object[] {false, 0, this.RenderPartialViewToString("_EntryCreateFormPartial", model)});
        }

Answer 1

To solve this I inherited from JsonResult and added the textarea there

using System;
using System.Web.Mvc;
using System.Web.Script.Serialization;

namespace TinyHouseMap.Web.Infrastructure.Results
{
    public class JsonInIframeResult : JsonResult
    {
        public bool EncloseInTextArea
        {
            get;
            set;
        }

        public override void ExecuteResult(ControllerContext context)
        {
            if (context == null)
            {
                throw new ArgumentNullException("context");
            }

            if ((JsonRequestBehavior == JsonRequestBehavior.DenyGet)
                && string.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
            {
                throw new InvalidOperationException("JsonRequest GetNotAllowed");
            }

            var response = context.HttpContext.Response;

            response.ContentType = !string.IsNullOrEmpty(ContentType) ? ContentType : "application/json";

            if (ContentEncoding != null)
            {
                response.ContentEncoding = ContentEncoding;
            }

            if (Data != null)
            {
                var serializer = new JavaScriptSerializer();

                string results;
                if (EncloseInTextArea)
                {
                    results = "<textarea>" + serializer.Serialize(Data) + "</textarea>";
                }
                else
                {
                    results = serializer.Serialize(Data);
                }


                response.Write(results);
            }
        }
    }
}

And then created a helper in my controller base class

protected JsonInIframeResult JsonInIframe(object data, string contentType, bool encloseInTextArea)
    {
        var result = new JsonInIframeResult {Data = data, ContentType = contentType, EncloseInTextArea = encloseInTextArea};
        return result;
    }