Difference between MvcHtmlString.Create() and Html.Raw()

This is an excellent opportunity to look at the source code that's available to us for ASP.NET (https://github.com/aspnet/AspNetWebStack/).

Looking at HtmlHelper.cs, this is the code for Html.Raw():

public IHtmlString Raw(string value)
{
    return new HtmlString(value);
}

public IHtmlString Raw(object value)
{
    return new HtmlString(value == null ? null : value.ToString());
}

And this is the code for the MvcHtmlString class:

namespace System.Web.Mvc
{
    public sealed class MvcHtmlString : HtmlString
    {
        [SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes", Justification = "MvcHtmlString is immutable")]
        public static readonly MvcHtmlString Empty = Create(String.Empty);

        private readonly string _value;

        public MvcHtmlString(string value)
            : base(value ?? String.Empty)
        {
            _value = value ?? String.Empty;
        }

        public static MvcHtmlString Create(string value)
        {
            return new MvcHtmlString(value);
        }

        public static bool IsNullOrEmpty(MvcHtmlString value)
        {
            return (value == null || value._value.Length == 0);
        }
    }
}

The most significant difference is that Html.Raw() accepts any object, while MvcHtmlString.Create() only accepts strings. Also, Html.Raw() returns an interface, while the Create method returns an MvcHtmlString object. Lastly, the Create deals with null differently.

There is no practical difference.

The MvcHtmlString.Create creates an instance of MvcHtmlString, while the Html.Raw method creates an instance of HtmlString, but MvcHtmlString just inherits from HtmlString, so they work the same.