Null check the model when working with nancy's super simple view engine.

NullCheckMatcher.cs

using System.Text.RegularExpressions;
using Nancy.ViewEngines.SuperSimpleViewEngine;

namespace Residata.Analysis.Web.Infrastructure {
    /// <summary>
    /// Null Check Matcher for the super simple view engine.
    /// 
    /// This checks if the model is null - or not!
    /// </summary>
    /// <example>
    /// @IsNull
    ///     Ops, could not find the requested object :-(
    /// @EndIsNull
    /// 
    /// @IsNotNull
    ///     Found it :-)
    /// @EndIsNull
    /// </example>
    public class NullCheckMatcher : ISuperSimpleViewEngineMatcher {
        private static readonly Regex NullCheckRegEx = new Regex(@"@(?<Type>IsNull|IsNotNull);?(?<Contents>.*?)@EndIsNull;?", RegexOptions.Singleline | RegexOptions.Compiled);
    
        public string Invoke(string content, dynamic model, IViewEngineHost host) {
            return NullCheckRegEx.Replace(content, x => {
                var type = x.Groups["Type"].Value;
                var contents = x.Groups["Contents"].Value;

                if (type == "IsNull") {
                    if (model == null) {
                        return contents;
                    }
                }
                else if (type == "IsNotNull") {
                    if (model != null) {
                        return contents;
                    }
                }

                return string.Empty;
            });
        }
    }
}