diff --git a/examples/WireMock.Net.ConsoleApplication/Program.cs b/examples/WireMock.Net.ConsoleApplication/Program.cs
index d34c5650..e312b7df 100644
--- a/examples/WireMock.Net.ConsoleApplication/Program.cs
+++ b/examples/WireMock.Net.ConsoleApplication/Program.cs
@@ -18,17 +18,26 @@ namespace WireMock.Net.ConsoleApplication
             Console.WriteLine("FluentMockServer running at {0}", server.Port);
 
             server
-              .Given(
-                Request
-                    .WithUrl("/*")
-                    .UsingGet()
-              )
-              .RespondWith(
-                Response
-                  .WithStatusCode(200)
-                  .WithHeader("Content-Type", "application/json")
-                  .WithBody(@"{ ""msg"": ""Hello world!""}")
-              );
+                .Given(Request.WithUrl(u => u.Contains("x")).UsingGet())
+                .RespondWith(Response
+                    .WithStatusCode(200)
+                    .WithHeader("Content-Type", "application/json")
+                    .WithBody(@"{ ""result"": ""/x with FUNC 200""}"));
+
+            server
+                .Given(Request.WithUrl("/*").UsingGet())
+                .RespondWith(Response
+                    .WithStatusCode(200)
+                    .WithHeader("Content-Type", "application/json")
+                    .WithBody(@"{ ""msg"": ""Hello world!""}")
+                );
+
+            server
+                .Given(Request.WithUrl("/data").UsingPost().WithBody(b => b.Contains("e")))
+                .RespondWith(Response
+                    .WithStatusCode(201)
+                    .WithHeader("Content-Type", "application/json")
+                    .WithBody(@"{ ""result"": ""data posted with FUNC 201""}"));
 
             server
                 .Given(Request.WithUrl("/data").UsingPost())
@@ -42,12 +51,11 @@ namespace WireMock.Net.ConsoleApplication
                 .RespondWith(Response
                     .WithStatusCode(200)
                     .WithHeader("Content-Type", "application/json")
-                    .WithBody(@"{ ""result"": ""data deleted with 201""}"));
+                    .WithBody(@"{ ""result"": ""data deleted with 200""}"));
 
             Console.WriteLine("Press any key to stop the server");
             Console.ReadKey();
 
-
             Console.WriteLine("Displaying all requests");
             var allRequests = server.RequestLogs;
             Console.WriteLine(JsonConvert.SerializeObject(allRequests, Formatting.Indented));
diff --git a/src/WireMock/Http/Ports.cs b/src/WireMock/Http/Ports.cs
index 4d5c2e1e..4fa6d268 100644
--- a/src/WireMock/Http/Ports.cs
+++ b/src/WireMock/Http/Ports.cs
@@ -1,16 +1,6 @@
-using System.Diagnostics.CodeAnalysis;
-using System.Net;
+using System.Net;
 using System.Net.Sockets;
 
-[module:
-    SuppressMessage("StyleCop.CSharp.DocumentationRules",
-        "SA1633:FileMustHaveHeader",
-        Justification = "Reviewed. Suppression is OK here, as unknown copyright and company.")]
-[module:
-    SuppressMessage("StyleCop.CSharp.DocumentationRules",
-        "SA1650:ElementDocumentationMustBeSpelledCorrectly",
-        Justification = "Reviewed. Suppression is OK here.")]
-
 namespace WireMock.Http
 {
     /// <summary>
@@ -24,15 +14,21 @@ namespace WireMock.Http
         /// <returns>
         /// The <see cref="int"/>.
         /// </returns>
-        /// <remarks>see http://stackoverflow.com/questions/138043/find-the-next-tcp-port-in-net. </remarks>
-        // ReSharper disable once StyleCop.SA1650
+        /// <remarks>see http://stackoverflow.com/questions/138043/find-the-next-tcp-port-in-net.</remarks>
         public static int FindFreeTcpPort()
         {
-            TcpListener l = new TcpListener(IPAddress.Loopback, 0);
-            l.Start();
-            int port = ((IPEndPoint)l.LocalEndpoint).Port;
-            l.Stop();
-            return port;
+            TcpListener tcpListener = null;
+            try
+            {
+                tcpListener = new TcpListener(IPAddress.Loopback, 0);
+                tcpListener.Start();
+
+                return ((IPEndPoint)tcpListener.LocalEndpoint).Port;
+            }
+            finally
+            {
+                tcpListener?.Stop();
+            }
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/WireMock/Http/TinyHttpServer.cs b/src/WireMock/Http/TinyHttpServer.cs
index 23f3bcbe..38b1fa26 100644
--- a/src/WireMock/Http/TinyHttpServer.cs
+++ b/src/WireMock/Http/TinyHttpServer.cs
@@ -53,13 +53,6 @@ namespace WireMock.Http
         {
             _httpHandler = httpHandler;
 
-            // .Net Framework is not supportted on XP or Server 2003, so no need for the check
-            /*if (!HttpListener.IsSupported)
-            {
-                Console.WriteLine("Windows XP SP2 or Server 2003 is required to use the HttpListener class.");
-                return;
-            }*/
-
             // Create a listener.
             _listener = new HttpListener();
             _listener.Prefixes.Add(urlPrefix);
diff --git a/src/WireMock/RequestBodySpec.cs b/src/WireMock/RequestBodySpec.cs
index 5dc7b60f..4e4f5daf 100644
--- a/src/WireMock/RequestBodySpec.cs
+++ b/src/WireMock/RequestBodySpec.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Text.RegularExpressions;
 using JetBrains.Annotations;
@@ -29,6 +30,11 @@ namespace WireMock
         /// </summary>
         private readonly Regex bodyRegex;
 
+        /// <summary>
+        /// The body function
+        /// </summary>
+        private readonly Func<string, bool> bodyFunc;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="RequestBodySpec"/> class.
         /// </summary>
@@ -41,6 +47,18 @@ namespace WireMock
             bodyRegex = new Regex(body);
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RequestBodySpec"/> class.
+        /// </summary>
+        /// <param name="func">
+        /// The body func.
+        /// </param>
+        public RequestBodySpec([NotNull] Func<string, bool> func)
+        {
+            Check.NotNull(func, nameof(func));
+            bodyFunc = func;
+        }
+
         /// <summary>
         /// The is satisfied by.
         /// </summary>
@@ -52,7 +70,7 @@ namespace WireMock
         /// </returns>
         public bool IsSatisfiedBy(RequestMessage requestMessage)
         {
-            return bodyRegex.IsMatch(requestMessage.Body);
+            return bodyRegex?.IsMatch(requestMessage.Body) ?? bodyFunc(requestMessage.Body);
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/WireMock/RequestBuilders/IBodyRequestBuilder.cs b/src/WireMock/RequestBuilders/IBodyRequestBuilder.cs
index b1134a3c..bd7f6504 100644
--- a/src/WireMock/RequestBuilders/IBodyRequestBuilder.cs
+++ b/src/WireMock/RequestBuilders/IBodyRequestBuilder.cs
@@ -1,4 +1,6 @@
-namespace WireMock.RequestBuilders
+using System;
+
+namespace WireMock.RequestBuilders
 {
     /// <summary>
     /// The BodyRequestBuilder interface.
@@ -15,5 +17,16 @@
         /// The <see cref="ISpecifyRequests"/>.
         /// </returns>
         ISpecifyRequests WithBody(string body);
+        
+        /// <summary>
+        /// The with body.
+        /// </summary>
+        /// <param name="body">
+        /// The body function.
+        /// </param>
+        /// <returns>
+        /// The <see cref="ISpecifyRequests"/>.
+        /// </returns>
+        ISpecifyRequests WithBody(Func<string, bool> body);
     }
 }
\ No newline at end of file
diff --git a/src/WireMock/RequestBuilders/IHeadersRequestBuilder.cs b/src/WireMock/RequestBuilders/IHeadersRequestBuilder.cs
index 7595f30a..2de9e2e5 100644
--- a/src/WireMock/RequestBuilders/IHeadersRequestBuilder.cs
+++ b/src/WireMock/RequestBuilders/IHeadersRequestBuilder.cs
@@ -1,4 +1,8 @@
-namespace WireMock.RequestBuilders
+using System;
+using System.Collections.Generic;
+using JetBrains.Annotations;
+
+namespace WireMock.RequestBuilders
 {
     /// <summary>
     /// The HeadersRequestBuilder interface.
@@ -19,5 +23,16 @@
         /// The <see cref="IHeadersRequestBuilder"/>.
         /// </returns>
         IHeadersRequestBuilder WithHeader(string name, string value, bool ignoreCase = true);
+
+        /// <summary>
+        /// The with header.
+        /// </summary>
+        /// <param name="func">
+        ///     The headers func.
+        /// </param>
+        /// <returns>
+        /// The <see cref="IHeadersRequestBuilder"/>.
+        /// </returns>
+        IHeadersRequestBuilder WithHeader([NotNull] Func<IDictionary<string, string>, bool> func);
     }
 }
\ No newline at end of file
diff --git a/src/WireMock/RequestBuilders/IParamsRequestBuilder.cs b/src/WireMock/RequestBuilders/IParamsRequestBuilder.cs
index 2a639694..40a8f684 100644
--- a/src/WireMock/RequestBuilders/IParamsRequestBuilder.cs
+++ b/src/WireMock/RequestBuilders/IParamsRequestBuilder.cs
@@ -1,4 +1,8 @@
-namespace WireMock.RequestBuilders
+using System;
+using System.Collections.Generic;
+using JetBrains.Annotations;
+
+namespace WireMock.RequestBuilders
 {
     /// <summary>
     /// The ParametersRequestBuilder interface.
@@ -17,6 +21,17 @@
         /// <returns>
         /// The <see cref="ISpecifyRequests"/>.
         /// </returns>
-        ISpecifyRequests WithParam(string key, params string[] values);
+        ISpecifyRequests WithParam([NotNull] string key, params string[] values);
+
+        /// <summary>
+        /// The with parameters.
+        /// </summary>
+        /// <param name="func">
+        /// The func.
+        /// </param>
+        /// <returns>
+        /// The <see cref="ISpecifyRequests"/>.
+        /// </returns>
+        ISpecifyRequests WithParam([NotNull] Func<IDictionary<string, List<string>>, bool> func);
     }
 }
\ No newline at end of file
diff --git a/src/WireMock/RequestBuilders/Request.cs b/src/WireMock/RequestBuilders/Request.cs
index d0e23098..76a4d177 100644
--- a/src/WireMock/RequestBuilders/Request.cs
+++ b/src/WireMock/RequestBuilders/Request.cs
@@ -1,6 +1,8 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using JetBrains.Annotations;
 
 [module:
     SuppressMessage("StyleCop.CSharp.ReadabilityRules",
@@ -54,10 +56,25 @@ namespace WireMock.RequestBuilders
         /// </returns>
         public static IVerbRequestBuilder WithUrl(string url)
         {
-            var specs = new List<ISpecifyRequests>();
-            var requests = new Request(specs);
-            specs.Add(new RequestUrlSpec(url));
-            return requests;
+            var specs = new List<ISpecifyRequests> { new RequestUrlSpec(url) };
+
+            return new Request(specs);
+        }
+
+        /// <summary>
+        /// The with url.
+        /// </summary>
+        /// <param name="func">
+        /// The url func.
+        /// </param>
+        /// <returns>
+        /// The <see cref="IVerbRequestBuilder"/>.
+        /// </returns>
+        public static IVerbRequestBuilder WithUrl(Func<string, bool> func)
+        {
+            var specs = new List<ISpecifyRequests> { new RequestUrlSpec(func) };
+
+            return new Request(specs);
         }
 
         /// <summary>
@@ -71,10 +88,25 @@ namespace WireMock.RequestBuilders
         /// </returns>
         public static IVerbRequestBuilder WithPath(string path)
         {
-            var specs = new List<ISpecifyRequests>();
-            var requests = new Request(specs);
-            specs.Add(new RequestPathSpec(path));
-            return requests;
+            var specs = new List<ISpecifyRequests> { new RequestPathSpec(path) };
+
+            return new Request(specs);
+        }
+
+        /// <summary>
+        /// The with path.
+        /// </summary>
+        /// <param name="func">
+        /// The path func.
+        /// </param>
+        /// <returns>
+        /// The <see cref="IVerbRequestBuilder"/>.
+        /// </returns>
+        public static IVerbRequestBuilder WithPath([NotNull] Func<string, bool> func)
+        {
+            var specs = new List<ISpecifyRequests> { new RequestPathSpec(func) };
+
+            return new Request(specs);
         }
 
         /// <summary>
@@ -178,6 +210,21 @@ namespace WireMock.RequestBuilders
             return this;
         }
 
+        /// <summary>
+        /// The with body.
+        /// </summary>
+        /// <param name="func">
+        /// The body function.
+        /// </param>
+        /// <returns>
+        /// The <see cref="ISpecifyRequests"/>.
+        /// </returns>
+        public ISpecifyRequests WithBody(Func<string, bool> func)
+        {
+            _requestSpecs.Add(new RequestBodySpec(func));
+            return this;
+        }
+
         /// <summary>
         /// The with parameters.
         /// </summary>
@@ -196,6 +243,21 @@ namespace WireMock.RequestBuilders
             return this;
         }
 
+        /// <summary>
+        /// The with parameters.
+        /// </summary>
+        /// <param name="func">
+        /// The func.
+        /// </param>
+        /// <returns>
+        /// The <see cref="ISpecifyRequests"/>.
+        /// </returns>
+        public ISpecifyRequests WithParam(Func<IDictionary<string, List<string>>, bool> func)
+        {
+            _requestSpecs.Add(new RequestParamSpec(func));
+            return this;
+        }
+
         /// <summary>
         /// The with header.
         /// </summary>
@@ -214,5 +276,20 @@ namespace WireMock.RequestBuilders
             _requestSpecs.Add(new RequestHeaderSpec(name, value, ignoreCase));
             return this;
         }
+
+        /// <summary>
+        /// The with header.
+        /// </summary>
+        /// <param name="func">
+        ///     The func.
+        /// </param>
+        /// <returns>
+        /// The <see cref="IHeadersRequestBuilder"/>.
+        /// </returns>
+        public IHeadersRequestBuilder WithHeader(Func<IDictionary<string, string>, bool> func)
+        {
+            _requestSpecs.Add(new RequestHeaderSpec(func));
+            return this;
+        }
     }
 }
diff --git a/src/WireMock/RequestHeaderSpec.cs b/src/WireMock/RequestHeaderSpec.cs
index 43e70172..b8bf9e47 100644
--- a/src/WireMock/RequestHeaderSpec.cs
+++ b/src/WireMock/RequestHeaderSpec.cs
@@ -1,6 +1,9 @@
-using System.Diagnostics.CodeAnalysis;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Text.RegularExpressions;
 using JetBrains.Annotations;
+using WireMock.Validation;
 
 [module:
     SuppressMessage("StyleCop.CSharp.ReadabilityRules",
@@ -33,6 +36,11 @@ namespace WireMock
         /// </summary>
         private readonly Regex patternRegex;
 
+        /// <summary>
+        /// The header function
+        /// </summary>
+        private readonly Func<IDictionary<string, string>, bool> headerFunc;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="RequestHeaderSpec"/> class.
         /// </summary>
@@ -49,6 +57,18 @@ namespace WireMock
             patternRegex = ignoreCase ? new Regex(pattern, RegexOptions.IgnoreCase) : new Regex(pattern);
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RequestHeaderSpec"/> class.
+        /// </summary>
+        /// <param name="func">
+        /// The func.
+        /// </param>
+        public RequestHeaderSpec([NotNull] Func<IDictionary<string, string>, bool> func)
+        {
+            Check.NotNull(func, nameof(func));
+            headerFunc = func;
+        }
+
         /// <summary>
         /// The is satisfied by.
         /// </summary>
@@ -58,8 +78,11 @@ namespace WireMock
         /// <returns>
         /// The <see cref="bool"/>.
         /// </returns>
-        public bool IsSatisfiedBy([NotNull] RequestMessage requestMessage)
+        public bool IsSatisfiedBy(RequestMessage requestMessage)
         {
+            if (patternRegex == null)
+                return headerFunc(requestMessage.Headers);
+
             string headerValue = requestMessage.Headers[name];
             return patternRegex.IsMatch(headerValue);
         }
diff --git a/src/WireMock/RequestMessage.cs b/src/WireMock/RequestMessage.cs
index 2ac15c19..224b5152 100644
--- a/src/WireMock/RequestMessage.cs
+++ b/src/WireMock/RequestMessage.cs
@@ -18,8 +18,7 @@ using System.Linq;
     SuppressMessage("StyleCop.CSharp.DocumentationRules",
         "SA1650:ElementDocumentationMustBeSpelledCorrectly",
         Justification = "Reviewed. Suppression is OK here.")]
-// ReSharper disable ArrangeThisQualifier
-// ReSharper disable InconsistentNaming
+
 namespace WireMock
 {
     /// <summary>
@@ -30,7 +29,7 @@ namespace WireMock
         /// <summary>
         /// The _params.
         /// </summary>
-        private readonly Dictionary<string, List<string>> _params = new Dictionary<string, List<string>>();
+        private readonly IDictionary<string, List<string>> _params = new Dictionary<string, List<string>>();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="RequestMessage"/> class.
@@ -50,7 +49,7 @@ namespace WireMock
         /// <param name="headers">
         /// The headers.
         /// </param>
-        public RequestMessage(string path, string query, string verb, string body, IDictionary<string, string> headers)
+        public RequestMessage(string path, string query, string verb, string body, IDictionary<string, string> headers = null)
         {
             if (!string.IsNullOrEmpty(query))
             {
@@ -72,12 +71,14 @@ namespace WireMock
                             dict[key].Add(term.Split('=')[1]);
                             return dict;
                         });
+
+                Parameters = _params;
             }
 
             Path = path;
-            Headers = headers; //.ToDictionary(kv => kv.Key.ToLower(), kv => kv.Value.ToLower());
+            Headers = headers;
             Verb = verb.ToLower();
-            Body = body?.Trim() ?? string.Empty;
+            Body = body;
         }
 
         /// <summary>
@@ -111,6 +112,11 @@ namespace WireMock
         /// </summary>
         public IDictionary<string, string> Headers { get; }
 
+        /// <summary>
+        /// Gets the parameters.
+        /// </summary>
+        public IDictionary<string, List<string>> Parameters { get; }
+
         /// <summary>
         /// Gets the body.
         /// </summary>
@@ -130,4 +136,4 @@ namespace WireMock
             return _params.ContainsKey(key) ? _params[key] : new List<string>();
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/WireMock/RequestParamSpec.cs b/src/WireMock/RequestParamSpec.cs
index 065f6658..e1bc2100 100644
--- a/src/WireMock/RequestParamSpec.cs
+++ b/src/WireMock/RequestParamSpec.cs
@@ -1,7 +1,9 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using JetBrains.Annotations;
+using WireMock.Validation;
 
 [module:
     SuppressMessage("StyleCop.CSharp.ReadabilityRules",
@@ -15,8 +17,7 @@ using JetBrains.Annotations;
     SuppressMessage("StyleCop.CSharp.DocumentationRules",
         "SA1633:FileMustHaveHeader",
         Justification = "Reviewed. Suppression is OK here, as unknown copyright and company.")]
-// ReSharper disable ArrangeThisQualifier
-// ReSharper disable InconsistentNaming
+
 namespace WireMock
 {
     /// <summary>
@@ -32,7 +33,9 @@ namespace WireMock
         /// <summary>
         /// The _values.
         /// </summary>
-        private readonly List<string> _values;
+        private readonly IEnumerable<string> _values;
+
+        private readonly Func<IDictionary<string, List<string>>, bool> _func;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="RequestParamSpec"/> class.
@@ -43,12 +46,27 @@ namespace WireMock
         /// <param name="values">
         /// The values.
         /// </param>
-        public RequestParamSpec(string key, List<string> values)
+        public RequestParamSpec([NotNull] string key, [NotNull] IEnumerable<string> values)
         {
+            Check.NotNull(key, nameof(key));
+            Check.NotNull(values, nameof(values));
+
             _key = key;
             _values = values;
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RequestParamSpec"/> class.
+        /// </summary>
+        /// <param name="func">
+        /// The func.
+        /// </param>
+        public RequestParamSpec([NotNull] Func<IDictionary<string, List<string>>, bool> func)
+        {
+            Check.NotNull(func, nameof(func));
+            _func = func;
+        }
+
         /// <summary>
         /// The is satisfied by.
         /// </summary>
@@ -58,9 +76,14 @@ namespace WireMock
         /// <returns>
         /// The <see cref="bool"/>.
         /// </returns>
-        public bool IsSatisfiedBy([NotNull] RequestMessage requestMessage)
+        public bool IsSatisfiedBy(RequestMessage requestMessage)
         {
-            return requestMessage.GetParameter(_key).Intersect(_values).Count() == _values.Count;
+            if (_func != null)
+            {
+                return _func(requestMessage.Parameters);
+            }
+
+            return requestMessage.GetParameter(_key).Intersect(_values).Count() == _values.Count();
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/WireMock/RequestPathSpec.cs b/src/WireMock/RequestPathSpec.cs
index c1e56f60..6a83848e 100644
--- a/src/WireMock/RequestPathSpec.cs
+++ b/src/WireMock/RequestPathSpec.cs
@@ -1,4 +1,5 @@
-using System.Diagnostics.CodeAnalysis;
+using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Text.RegularExpressions;
 using JetBrains.Annotations;
 using WireMock.Validation;
@@ -15,8 +16,7 @@ using WireMock.Validation;
     SuppressMessage("StyleCop.CSharp.DocumentationRules",
         "SA1633:FileMustHaveHeader",
         Justification = "Reviewed. Suppression is OK here, as unknown copyright and company.")]
-// ReSharper disable ArrangeThisQualifier
-// ReSharper disable InconsistentNaming
+
 namespace WireMock
 {
     /// <summary>
@@ -25,9 +25,14 @@ namespace WireMock
     public class RequestPathSpec : ISpecifyRequests
     {
         /// <summary>
-        /// The _path.
+        /// The pathRegex.
         /// </summary>
-        private readonly Regex _path;
+        private readonly Regex pathRegex;
+
+        /// <summary>
+        /// The url function
+        /// </summary>
+        private readonly Func<string, bool> pathFunc;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="RequestPathSpec"/> class.
@@ -38,7 +43,19 @@ namespace WireMock
         public RequestPathSpec([NotNull, RegexPattern] string path)
         {
             Check.NotNull(path, nameof(path));
-            _path = new Regex(path);
+            pathRegex = new Regex(path);
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RequestPathSpec"/> class.
+        /// </summary>
+        /// <param name="func">
+        /// The url func.
+        /// </param>
+        public RequestPathSpec([NotNull] Func<string, bool> func)
+        {
+            Check.NotNull(func, nameof(func));
+            pathFunc = func;
         }
 
         /// <summary>
@@ -50,9 +67,9 @@ namespace WireMock
         /// <returns>
         /// The <see cref="bool"/>.
         /// </returns>
-        public bool IsSatisfiedBy([NotNull] RequestMessage requestMessage)
+        public bool IsSatisfiedBy(RequestMessage requestMessage)
         {
-            return _path.IsMatch(requestMessage.Path);
+            return pathRegex?.IsMatch(requestMessage.Path) ?? pathFunc(requestMessage.Path);
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/WireMock/RequestUrlSpec.cs b/src/WireMock/RequestUrlSpec.cs
index e0abe499..06f8d981 100644
--- a/src/WireMock/RequestUrlSpec.cs
+++ b/src/WireMock/RequestUrlSpec.cs
@@ -1,4 +1,5 @@
-using System.Diagnostics.CodeAnalysis;
+using System;
+using System.Diagnostics.CodeAnalysis;
 using JetBrains.Annotations;
 using System.Text.RegularExpressions;
 using WireMock.Validation;
@@ -29,6 +30,11 @@ namespace WireMock
         /// </summary>
         private readonly Regex urlRegex;
 
+        /// <summary>
+        /// The url function
+        /// </summary>
+        private readonly Func<string, bool> urlFunc;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="RequestUrlSpec"/> class.
         /// </summary>
@@ -41,6 +47,18 @@ namespace WireMock
             urlRegex = new Regex(url);
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RequestUrlSpec"/> class.
+        /// </summary>
+        /// <param name="func">
+        /// The url func.
+        /// </param>
+        public RequestUrlSpec(Func<string, bool> func)
+        {
+            Check.NotNull(func, nameof(func));
+            urlFunc = func;
+        }
+
         /// <summary>
         /// The is satisfied by.
         /// </summary>
@@ -52,7 +70,7 @@ namespace WireMock
         /// </returns>
         public bool IsSatisfiedBy(RequestMessage requestMessage)
         {
-            return urlRegex.IsMatch(requestMessage.Url);
+            return urlRegex?.IsMatch(requestMessage.Url) ?? urlFunc(requestMessage.Url);
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/WireMock/ResponseMessage.cs b/src/WireMock/ResponseMessage.cs
index 24963cbe..4836aa17 100644
--- a/src/WireMock/ResponseMessage.cs
+++ b/src/WireMock/ResponseMessage.cs
@@ -28,16 +28,6 @@ namespace WireMock
         /// </summary>
         private readonly IDictionary<string, string> _headers = new ConcurrentDictionary<string, string>();
 
-        /// <summary>
-        /// The status code.
-        /// </summary>
-        private volatile int statusCode = 200;
-
-        /// <summary>
-        /// The body.
-        /// </summary>
-        private volatile string body;
-
         /// <summary>
         /// Gets the headers.
         /// </summary>
@@ -46,34 +36,12 @@ namespace WireMock
         /// <summary>
         /// Gets or sets the status code.
         /// </summary>
-        public int StatusCode
-        {
-            get
-            {
-                return statusCode;
-            }
-
-            set
-            {
-                statusCode = value;
-            }
-        }
+        public int StatusCode { get; set; } = 200;
 
         /// <summary>
         /// Gets or sets the body.
         /// </summary>
-        public string Body
-        {
-            get
-            {
-                return body;
-            }
-
-            set
-            {
-                body = value;
-            }
-        }
+        public string Body { get; set; }
 
         /// <summary>
         /// The add header.
diff --git a/test/WireMock.Net.Tests/FluentMockServerTests.cs b/test/WireMock.Net.Tests/FluentMockServerTests.cs
index 2c15b19a..05f85155 100644
--- a/test/WireMock.Net.Tests/FluentMockServerTests.cs
+++ b/test/WireMock.Net.Tests/FluentMockServerTests.cs
@@ -86,7 +86,7 @@ namespace WireMock.Net.Tests
             Check.That(_server.RequestLogs).HasSize(1);
             var requestLogged = _server.RequestLogs.First();
             Check.That(requestLogged.Verb).IsEqualTo("get");
-            Check.That(requestLogged.Body).IsEmpty();
+            Check.That(requestLogged.Body).IsNull();
         }
 
         [Test]
diff --git a/test/WireMock.Net.Tests/RequestsTests.cs b/test/WireMock.Net.Tests/RequestsTests.cs
index 9d138923..d754f90a 100644
--- a/test/WireMock.Net.Tests/RequestsTests.cs
+++ b/test/WireMock.Net.Tests/RequestsTests.cs
@@ -265,6 +265,19 @@ namespace WireMock.Net.Tests
             Check.That(spec.IsSatisfiedBy(request)).IsTrue();
         }
 
+        [Test]
+        public void Should_specify_requests_matching_given_params_func()
+        {
+            // given
+            var spec = Request.WithPath("/foo").WithParam(p => p.ContainsKey("bar") && (p["bar"].Contains("1") || p["bar"].Contains("2")));
+
+            // when
+            var request = new RequestMessage("/foo", "bar=1&bar=2", "Get", "Hello world!", new Dictionary<string, string>());
+
+            // then
+            Check.That(spec.IsSatisfiedBy(request)).IsTrue();
+        }
+
         [Test]
         public void Should_exclude_requests_not_matching_given_params()
         {