Razor allow custom html builders to use @ syntax and not encode the output

gistfile1.cs

// Out of the box, WebViewPage essentially does this to write content:

    Output.Write(HttpUtility.HtmlEncode(content));
    
// And HttpUtility.HtmlEncode will encode anything not marked with the IHtmlString interface
// If we have a custom html builder we have to use something like this:

    @Html.Raw(safeBuilder)
    
// This is a lot of extra typing
// I like that it's explicit that it's Raw html but we are using a safe builder so we shouldn't need the ceremony simply because our safe builder isn't marked with IHtmlString.
// This can happen if we're using a builder from a 3rd party library and we can't change the code or if we don't want to take a dependency to IHtmlString.

// But we can work around this!

// Here's a fake html builder

	public class MySafeHtmlBuilder
	{
		private readonly string _Html;

		public MySafeHtmlBuilder(string html)
		{
			_Html = html;
		}

		public override string ToString()
		{
			return _Html;
		}
	}

// And here's using it in a view

    @(new MySafeHtmlBuilder("<span>hi</span>"))

// And to make it work, setup a custom razor WebViewPage. 
// The magic is in overriding Write and if your custom type is detected, to just write it to the output directly

	public abstract class MyRazorPage<TModel> : WebViewPage<TModel>
	{
		public override void Write(object value)
		{
			if (value is MySafeHtmlBuilder)
			{
				Output.Write(value);
				return;
			}

			base.Write(value);
		}
	}

// Don't forget to update your razor config in the Web.Config in your views folder

    <pages pageBaseType="Namespace.MyRazorPage">

// FYI this is a POC, I haven't had much chance to use it extensively in reality, but it should suffice

// Warning: make sure you are actually producing safe html, or you'll be vulnerable to XSS attacks!

// DO NOT DO THINGS LIKE THIS!!!:

    public override void Write(object value)
    {
        Output.Write(value);
    }