Question

I want to manipulate HTML using a custom view engine like this:

protected override void RenderView(ViewContext viewContext, TextWriter writer, object instance)
{
    if (viewContext.Controller is MyController)
    {
       .. alter the html then write to writer
    } else {
        base.RenderView(viewContext, writer, instance);
    }
}

RenderView gets called for the view and each partial view, but I can’t figure out a reliable way to determine whether it’s rendering the outer view or a partial view.

The type of the writer object is HttpWriter for a partial view and StringWriter for the outer view. This seems like a bad way to test it, but so far it’s the only concrete thing I can find

The instance tells me the view or partial view name, but checking a string to see if I’m rendering a partial view or not seems brittle.

Is there any more direct way to determine if it’s a partial view or not?

Answer 1

You could pass a boolean parameter to your custom view from your custom view engine:

public class MyRazorView : RazorView
{
    private readonly bool _isPartial;

    public MyRazorView(ControllerContext controllerContext, string viewPath, string layoutPath, bool runViewStartPages, IEnumerable<string> viewStartFileExtensions, IViewPageActivator viewPageActivator, bool isPartial)
        : base(controllerContext, viewPath, layoutPath, runViewStartPages, viewStartFileExtensions, viewPageActivator)
    {
        _isPartial = isPartial;
    }

    protected override void RenderView(ViewContext viewContext, TextWriter writer, object instance)
    {
        if (viewContext.Controller is MyController)
        {
            if (_isPartial)
            {
                // it's a partial
            }
            else
            {
                // it's the main view
            }
        } 
        base.RenderView(viewContext, writer, instance);
    }
}

public class MyRazorViewEngine : RazorViewEngine
{
    protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath)
    {
        return new MyRazorView(
            controllerContext, 
            partialPath, 
            null, 
            false, 
            base.FileExtensions, 
            base.ViewPageActivator, 
            true
        );
    }

    protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath)
    {
        return new MyRazorView(
            controllerContext, 
            viewPath, 
            masterPath, 
            true, 
            base.FileExtensions, 
            base.ViewPageActivator, 
            false
        );
    }
}