A Better MIME Mapping Stealer!

In the interest of self-improvement and sharing knowledge, I felt that I should share an update to my last post. I discovered a slightly better way to create the GetMimeMapping delegate/method via reflection that involves less casting and overhead, and is more Object Oriented in a sense. It allows the signature of the reflected method to be Func<string, string> instead of MethodInfo. Code below, note the use of Delegate.CreateDelegate(Type, MethodInfo):

/// <summary>
/// Exposes the Mime Mapping method that Microsoft hid from us.
/// </summary>
public static class MimeMappingStealer
{
    // The get mime mapping method
    private static readonly Func<string, string> _getMimeMappingMethod = null;

    /// <summary>
    /// Static constructor sets up reflection.
    /// </summary>
    static MimeMappingStealer()
    {
        // Load hidden mime mapping class and method from System.Web
        var assembly = Assembly.GetAssembly(typeof(HttpApplication));
        Type mimeMappingType = assembly.GetType("System.Web.MimeMapping");
        _getMimeMappingMethod = 
		    (Func<string, string>)Delegate.CreateDelegate(typeof(Func<string, string>), 
			    mimeMappingType.GetMethod("GetMimeMapping", 
                BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public |
                BindingFlags.NonPublic | BindingFlags.FlattenHierarchy));
    }

    /// <summary>
    /// Exposes the hidden Mime mapping method.
    /// </summary>
    /// <param name="fileName">The file name.</param>
    /// <returns>The mime mapping.</returns>
    public static string GetMimeMapping(string fileName)
    {
        return _getMimeMappingMethod(fileName);
    }
}