CODEWITHSUNDEEP
asp.net-mvcasp.net-mvc-3razor
Chao
Chao

Reputation: 3043

Returning the text of a Partial

Part of my MVC application includes a wiki. As well as the standard wiki formatting there are a number of special tags for rendering data into templates. When parsing these tags it gets the data from the repository, instantiates a viewmodel and renders it to a partial, this partial then gets inserted into the markup replacing the original tag. The finalised markup itself is rendered as part of a DisplayFor in any properties with the relevant UIHint.

The relevant part of the code is:

private static void MatchSpecial(WikiHelper wh)
    {
        wh.match = SpecialTagRegex.Match(wh.sb.ToString());
        while (wh.match.Success)
        {
            wh.sb.Remove(wh.match.Index, wh.match.Length);
            string[] args = wh.match.Groups[2].Value.Split('|');
            switch (wh.match.Groups[1].Value.ToUpperInvariant())
            {
                case "IMAGE":
                    string imageid;

                    imageid = args[0];
                    Image i = baserepo.imagerepo.GetImage(imageid);
                    ViewModels.ImageViewModel ivm = new ViewModels.ImageViewModel(i, args);
                    wh.sb.Insert(wh.match.Index, wh.Html.Partial("ImageViewModel",ivm));
                    break;
            }
            wh.match = SpecialTagRegex.Match(wh.sb.ToString(), ws.end);
        }
    }

The relevant members of WikiHelper are:

wh.sb - StringBuilder containing the markup
wh.html - the HtmlHelper from the main view
wh.match - holds the current regex matches

In MVC2 this worked fine. I'm now in the process of upgrading to MVC3 and the Razor ViewEngine. Despite the fact that Html.Partial is supposed to return the MvcHtmlString of the partial it is instead returning an empty string and writing the content directly into the response, which has the result of all similarly templated elements appearing at the very top of the HTML file (even before anything in my layout file).

Upvotes: 1

Views: 116

Answers (1)

Darin Dimitrov
Darin Dimitrov

Reputation: 1038820

Given the symptoms you are describing, I suspect that you are directly writing to the response stream somewhere in your custom helpers. So wherever you are outputing to the response make sure you replace:

htmlHelper.ViewContext.HttpContext.Response.Write("some string");

with:

htmlHelper.ViewContext.Writer.Write("some string");

Writing directly to the response stream worked in WebForms view engine because it is legacy from classic WebForms where this was how things were supposed to work. In ASP.NET MVC though this is incorrect. It worked but is incorrect. All helpers should be writing to ViewContext.Writer instead. Razor writes things into temporary buffers which are then flushed to the response. It uses an inside-out rendering.

Upvotes: 1

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