Sitecore 8 Webforms - Calling RenderControl() on Sublayout returns null

Question

I'm currently having some issues, while trying to render a sublayout programatically on the server-side. Basically, I want to render a sublayout found on the item myItem, that has a single rendering (sublayout) on it. The criteria is that it should render out correctly for normal mode and Experience Editor mode.

Currently, this is what I've done:

var builder = new StringBuilder();
using (StringWriter writer = new StringWriter(builder))      
using (HtmlTextWriter htmlWriter = new HtmlTextWriter(writer))
{

    var renderings = myItem.Visualization.GetRenderings(Sitecore.Context.Device, true);
    foreach (var rendering in renderings)
    {
        var renderControl = rendering.GetControl();

        rendering.Settings.DataSource = myItem.Paths.FullPath;

        renderControl.RenderControl(htmlWriter);
    }
}

var output = builder.ToString();

Looking at the output, this is empty. I've also tried just to call the RenderControl() and output it to a string, which is then set to null. I should also note, that I do have a PageContext in the control where this code is executed. I can also verify that I can add the renderControl as a child to a ASP placeholder control, which then renders out correctly - but only for preview mode, since is doesn't render the control out with support for the Experience Editor.

What am I missing?

Answer 1

While this is an example of rendering a Controller Rendering, I believe it will help you - the basic principles should be the same. Specifically I think, entering a RenderingContext is what you might be missing.

    public virtual HtmlString RenderItem(string idOrPath, string controller, string action)
    {
        Assert.ArgumentNotNullOrEmpty(idOrPath, nameof(idOrPath));
        Assert.ArgumentNotNullOrEmpty(controller, "controller");
        Assert.ArgumentNotNullOrEmpty(action, "action");
        var r = new Rendering();
        r.DataSource = idOrPath;

        return RenderItem(r, controller, action);
    }

    public virtual HtmlString RenderItem(Rendering rendering, string controller, string action)
    {
        Assert.ArgumentNotNull(rendering, nameof(rendering));
        Assert.ArgumentNotNullOrEmpty(controller, "controller");
        Assert.ArgumentNotNullOrEmpty(action, "action");

        using (RenderingContext.EnterContext(rendering))
        {
            var runner = new ControllerRunner(controller, action);
            var result = runner.Execute();
            return new HtmlString(result);
        }
    }

Answer 2

I ended up getting it working, but not using the RenderControl() method. It turns out, that I could just call the GetControl() to get the control for the sublayout afterall, and append that control to the child controls for the actual view. Moreover, I found that it was necessary to set the datasource, before calling the GetControl() method:

var renderings = myItem.Visualization.GetRenderings(Sitecore.Context.Device, true);
foreach (var rendering in renderings)
{
    rendering.Settings.DataSource = myItem.Paths.FullPath;

    Control control = rendering.GetControl();
    this.Controls.Add(control); // There 'this' refers to the actual View
}