The DiffPlex project is a combination of a .NET Diffing Library with a Silverlight and HTML diff viewer. It is released open source under the MS-PL license.

• The library allows developers to embed diffing functionality inside their applications or websites. (Click here to learn how to use the api)

• The Silverlight viewer allows real-time diffing of documents. (Click here to try it out)

• The website viewer shows how to embed diffing functionality inside of a website. (Click here to learn more)

Codeplex Page: http://snippetdesigner.codeplex.com/

Visual Studio Gallery Page: http://visualstudiogallery.msdn.microsoft.com/en-us/B08B0375-139E-41D7-AF9B-FAEE50F68392

This release contains several bug fixes but more importantly it now includes support for Visual Studio 2010.

I am super excited for this since now you can install the Snippet Designer from inside of Visual Studio using the new extension manager. Just open up the extension manager and search for “Snippet Designer”.

Then you just need to install it and restart Visual Studio.

Enjoy!

open Lexer
let definitions = 
    lexerDefinitions {
        do! addNextlineDefinition "NEWLINE" @"(\n\r)|\n|\r"
        do! addIgnoreDefinition "WS"        @"\s"
        do! addDefinition "LET"             "let"
        do! addDefinition "ID"              "(?i)[a-z][a-z0-9]*"
        do! addDefinition "FLOAT"           @"[0-9]+\.[0-9]+"
        do! addDefinition "INT"             "[0-9]+"
        do! addDefinition "OPERATOR"      @"[+*=!/&|<>\^\-]+"   
    }

With those defined you can execute the lexer with:

open Lexer
let lex input = 
    try    
        let y = Lexer.tokenize definitions input
        printfn "%A" y
    with e -> printf "%s" e.Message
lex "let a = 5"

Which will result in:

seq [{name = "LET";
      text = "let";
      pos = 0;
      column = 0;
      line = 0;}; {name = "ID";
                   text = "a";
                   pos = 4;
                   column = 4;
                   line = 0;}; {name = "OPERATOR";
                                text = "=";
                                pos = 6;
                                column = 6;
                                line = 0;}; {name = "INT";
                                             text = "5";
                                             pos = 8;
                                             column = 8;
                                             line = 0;}]

The lexer’s code is structured in three parts.  The first part is a state monad using the F# computation expressions.  This enables the declarative approach (seen above) to setup your lexer rules.

module StateMonad
type State<'s,'a> = State of ('s -> ('a *'s))
let runState (State f) = f
type StateBuilder() = 
    member b.Return(x) = State (fun s -> (x,s))
    member b.Delay(f) = f() : State<'s,'a>
    member b.Zero() = State (fun s -> ((),s))
    member b.Bind(State p,rest) = State (fun s -> let v,s2 = p s in  (runState (rest v)) s2)
    member b.Get () = State (fun s -> (s,s))
    member b.Put s = State (fun _ -> ((),s))

The second part are the combinators that are used to define your lexer rules.  There are three main combinators:  AddDefinition which lets you define a name / regex pair, AddIgnoreDefinition which lets you define characters which the lexer should ignore and AddNextlineDefinition which lets you define what characters determine a new line.

type LexDefinitions = 
  {regexes : string list;
   names : string list;
   nextlines : bool list;
   ignores : bool list; }
   
let buildDefinition name pattern nextLine ignore =
    state {
        let! x = state.Get()
        do! state.Put { regexes = x.regexes @  [sprintf @"(?<%s>%s)" name pattern];
                        names = x.names @ [name]; 
                        nextlines  = x.nextlines @ [nextLine];
                        ignores = x.ignores @ [ignore]}
    }
    
let addDefinition name pattern = buildDefinition name pattern false false
let addIgnoreDefinition name pattern = buildDefinition name pattern false true
let addNextlineDefinition name pattern = buildDefinition name pattern true true    

And the final part is the code that performs the tokenizing.  It uses the Seq.unfold method to create the list of tokens.  Unfold is a function which takes a single item and generates a list of new items from it.  It is the opposite of Seq.fold which takes a list of items and turns it into a single item.  The tokenize function used Seq.unfold to generate each token while keeping track of the current line number, position in that line and position in the input string.

type Token = 
    { name : string;
      text: string; 
      pos :int;
      column: int;
      line: int }
   
let createLexDefs pb =  (runState pb) {regexes = []; names = []; nextlines = []; ignores = []} |> snd
 
let tokenize lexerBuilder (str:string) = 
    let patterns = createLexDefs lexerBuilder
    let combinedRegex =  Regex(List.fold (fun acc reg -> acc + "|" + reg) (List.head patterns.regexes) (List.tail patterns.regexes))
    let nextlineMap = List.zip patterns.names patterns.nextlines |> Map.ofList
    let ignoreMap = List.zip patterns.names patterns.ignores |> Map.ofList
    let tokenizeStep (pos,line,lineStart) = 
        if pos >= str.Length then
            None
        else
            let getMatchedGroupName (grps:GroupCollection) names = List.find (fun (name:string) -> grps.[name].Length > 0) names
            match combinedRegex.Match(str, pos) with
                | mt when mt.Success && pos = mt.Index  -> 
                    let groupName = getMatchedGroupName mt.Groups patterns.names
                    let column = mt.Index - lineStart
                    let nextPos = pos + mt.Length
                    let (nextLine, nextLineStart) = if nextlineMap.Item groupName then (line + 1, nextPos) else (line,lineStart)
                    let token = if ignoreMap.Item groupName 
                                then None 
                                else Some {
                                        name = groupName; 
                                        text = mt.Value; 
                                        pos = pos; 
                                        line = line; 
                                        column = column; }
                    Some(token, (nextPos, nextLine, nextLineStart))
                    
                | otherwise -> 
                    let textAroundError = str.Substring(pos, min (pos + 5) str.Length)
                    raise (ArgumentException (sprintf "Lexing error occured at line:%d and column:%d near the text:%s" line (pos - lineStart) textAroundError))
    Seq.unfold tokenizeStep (0, 0, 0) |> Seq.filter (fun x -> x.IsSome) |> Seq.map (fun x -> x.Value)

Lastly, here are the unit tests written using XUnit.Net:

module LexerFacts
open Xunit
open Lexer
open System.Linq
let simpleDefs = 
    state {
        do! addNextlineDefinition "NextLine"           "/"
        do! addIgnoreDefinition "IgnoredSymbol"        "=+"
        do! addDefinition "String"                     "[a-zA-Z]+"
        do! addDefinition "Number"                     "\d+"
        do! addDefinition "Name"                       "Matt"
    }
[<Fact>]
let Will_return_no_tokens_for_empty_string() =
  
    let tokens = Lexer.tokenize simpleDefs ""
    
    Assert.Equal(0, tokens.Count())
[<Fact>]
let Will_throw_exception_for_invalid_token() =
  
    let tokens = Lexer.tokenize simpleDefs "-"
    let ex = Assert.ThrowsDelegateWithReturn(fun () -> upcast tokens.Count()) |> Record.Exception
    Assert.NotNull(ex)
    Assert.True(ex :? System.ArgumentException)
[<Fact>]
let Will_ignore_symbols_defined_as_ignore_symbols() =
  
    let tokens = Lexer.tokenize simpleDefs "========="
    
    Assert.Equal(0, tokens.Count())
[<Fact>]
let Will_get_token_with_correct_position_and_type() =
  
    let tokens = Lexer.tokenize simpleDefs "1one=2=two"
    
    Assert.Equal("Number",tokens.ElementAt(2).name)
    Assert.Equal("2",tokens.ElementAt(2).text)
    Assert.Equal(5,tokens.ElementAt(2).pos)
    Assert.Equal(5,tokens.ElementAt(2).column)
    Assert.Equal(0,tokens.ElementAt(2).line)
[<Fact>]
let Will_tokenize_string_with_alernating_numbers_and_strings() =
  
    let tokens = Lexer.tokenize simpleDefs "1one2two"
    
    Assert.Equal("1",tokens.ElementAt(0).text)
    Assert.Equal("one",tokens.ElementAt(1).text)
    Assert.Equal("2",tokens.ElementAt(2).text)
    Assert.Equal("two",tokens.ElementAt(3).text)
[<Fact>]
let Will_increment_line_with_newline_symbol() =
  
    let tokens = Lexer.tokenize simpleDefs "1one/2two"
    
    Assert.Equal("Number",tokens.ElementAt(2).name)
    Assert.Equal("2",tokens.ElementAt(2).text)
    Assert.Equal(5,tokens.ElementAt(2).pos)
    Assert.Equal(0,tokens.ElementAt(2).column)
    Assert.Equal(1,tokens.ElementAt(2).line)
[<Fact>]
let Will_give_priority_to_lexer_definitions_defined_earlier() =
  
    let tokens = Lexer.tokenize simpleDefs "Matt"
    
    Assert.Equal("String",tokens.ElementAt(0).name)

I attached a zip (Lexer.zip) containing all the code mentioned above.

ls * -recurse -include *.aspx, *.ascx, *.cs, *.ps1 | Get-Content | Measure-Object -Line

Just replace the file extensions with the ones you use in your project.

To be able to test the UrlHelper (since it doesn't have an interface or virtual methods) I wrote a simple wrapper around it with an interface to enable testing.  Using that with this extension method makes testing route generation a breeze.

Given a call to generate a Url like this:

var url = Url.RouteUrl("Show", new { projectName="matt" });

You can write a setup on your Mock of the Url helper using a similar syntax:

UrlHelperMock
.Setup(x => x.RouteUrl("Show",new{ projectName="matt"}.AsMatch()))
.Return("someUrlToTest");

Here is the code that defines the AsMatch extension method:

    public static class ObjectMoqExtensions
    {
        public static object AsMatch(this object @object)
        {
            return Match<object>.Create(testObject => DoObjectsMatch(@object, testObject));
        }
        private static bool DoObjectsMatch(object object1, object object2)
        {
            var props1 = ToDictionary(object1);
            var props2 = ToDictionary(object2);
            var query = from prop1 in props1
                        join prop2 in props2 on prop1.Key equals prop2.Key
                        select prop1.Value.Equals(prop2.Value);
            return query.Count(x => x) == Math.Max(props1.Count(), props2.Count());
        }
        public static Dictionary<string, object> ToDictionary(object @object)
        {
            var dictionary = new Dictionary<string, object>();
            var properties = TypeDescriptor.GetProperties(@object);
            foreach (PropertyDescriptor property in properties)
                dictionary.Add(property.Name, property.GetValue(@object));
            return dictionary;
        }
    }

The sample has code which converts HTML to and from a XAML Flow Document.  But this doesn’t make things easier until you realize that there is a way to convert RTF to XAML easily. The key is to use System.Windows.Controls.RichTextBox which can load RTF from a stream and save it as XAML.  This conversion is shown below:

        private static string ConvertRtfToXaml(string rtfText)
        {
            var richTextBox = new RichTextBox();
            if (string.IsNullOrEmpty(rtfText)) return "";
            var textRange = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);
            using (var rtfMemoryStream = new MemoryStream())
            {
                using (var rtfStreamWriter = new StreamWriter(rtfMemoryStream))
                {
                    rtfStreamWriter.Write(rtfText);
                    rtfStreamWriter.Flush();
                    rtfMemoryStream.Seek(0, SeekOrigin.Begin);
                    textRange.Load(rtfMemoryStream, DataFormats.Rtf);
                }
            }
            using (var rtfMemoryStream = new MemoryStream())
            {
                textRange = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);
                textRange.Save(rtfMemoryStream, DataFormats.Xaml);
                rtfMemoryStream.Seek(0, SeekOrigin.Begin);
                using (var rtfStreamReader = new StreamReader(rtfMemoryStream))
                {
                    return rtfStreamReader.ReadToEnd();
                }
            }
        }

With this code we have all we need to convert RTF to HTML. I modified the sample to add this RTF To XAML conversation and then I run that XAML through HTML converter which results in the HTML text. I added an interface to these conversion utilities and converted the sample into a library so that I would be able to use it from other projects.  Here is the interface:

 public interface IMarkupConverter
    {
        string ConvertXamlToHtml(string xamlText);
        string ConvertHtmlToXaml(string htmlText);
        string ConvertRtfToHtml(string rtfText);
    }
    public class MarkupConverter : IMarkupConverter
    {
        public string ConvertXamlToHtml(string xamlText)
        {
            return HtmlFromXamlConverter.ConvertXamlToHtml(xamlText, false);
        }
        public string ConvertHtmlToXaml(string htmlText)
        {
            return HtmlToXamlConverter.ConvertHtmlToXaml(htmlText, true);
        }
        public string ConvertRtfToHtml(string rtfText)
        {
            return RtfToHtmlConverter.ConvertRtfToHtml(rtfText);
        }
    }

With this I am now able to convert from RTF to HTML.  However, there is one catch - the conversion uses the RichTextBox WPF control which requires a single threaded apartment (STA).  Therefore in order to run your code that calls the ConvertRtfToHtml function, it must also be running in a STA.  If you can’t have your program run in a STA then you must create a new STA thread to run the conversion. Like this:

MarkupConverter markupConverter = new MarkupConverter();
private string ConvertRtfToHtml(string rtfText)
{
   var thread = new Thread(ConvertRtfInSTAThread);
   var threadData = new ConvertRtfThreadData { RtfText = rtfText };
   thread.SetApartmentState(ApartmentState.STA);
   thread.Start(threadData);
   thread.Join();
   return threadData.HtmlText;
}
private void ConvertRtfInSTAThread(object rtf)
{
   var threadData = rtf as ConvertRtfThreadData;
   threadData.HtmlText = markupConverter.ConvertRtfToHtml(threadData.RtfText);
}
        
private class ConvertRtfThreadData
{
   public string RtfText { get; set; }
   public string HtmlText { get; set; }
}

Here is the zip contain the code for the Markup converter: MarkupConverter.zip

var val = (SomeEnum)Enum.Parse(typeof(SomeEnum),”someString”);

I have typed this too many times and it annoys me. 

I wrote a small extension method on the string type to make this better:

public static class StringExtensions
{
    public static T ToEnum<T>(this string @string)
    {
        return (T)Enum.Parse(typeof (T), @string);
    }
}

With this I can now write the previous line as:

var val = "someString".ToEnum<SomeEnum>()

A test case should be like a simple short story.  The characters are introduced, action/conflict occurs and then resolution takes place (sometimes with a moral).  This (kind of) corresponds to the 3 steps of a unit test: arrange, act and assert.  You arrange and setup what you need for your test to run, you perform the action that you are trying to test and then you assert the results. The issue I find is that a coder, in attempting to apply DRY to his test cases, will abstract away all of the arrange step into a function often with a name like SetupExpectations or just Setup.  This goes against the point of a test case. A test case needs to be concise and tell me everything I need to know about how that one bit of functionality works. I don’t want to jump around the test class trying to read one test case. To me, this is like reading a book that says, “If you want to learn about the characters in this book please open this other book.”  This doesn’t stop you from understanding the test, but it slows you down…and is just annoying.

That is why I will come out and say do not apply DRY haphazardly to test cases.

I encountered this problem when I was a web developer in college for a late night student activities program aptly named  Late Nite Binghamton.  My co-worker and girlfriend Mallory was a graduate assistant for the program and had many ideas for how to make the website better and more engaging.  While working with her she would often see me typing in the hexadecimal color codes in css such as:

color: #F24A7D

As I am inept with what color look good (I often say that I never learnt colors) I would often ask her for help with picking out colors and I decided that if she was able to give me these colors in their hex color codes it would make us more efficient :) I sat her down and described to her how they work but after talking for a bit I realized that although she understood everything that I said she wouldn’t gain a feel for what hex numbers related to what colors just from hearing me talk.

In order to help her gain this feel I created a simple game called The Mallory Color Guessing Game.  The game is a webpage which shows you a large colored box and it is your job to guess what the hex color code is. 

After you guess it tells you how close you were to the actual color:

This game was a hit! Mallory loved it and she would compete with me to see who could guess the color the best.  Pretty quickly she gained a feel for what the hex digits meant and what color they represented. And that is how I taught my girlfriend hex!

NOTE: Mallory consistently gets over 80% at the Mallory Color Guessing Game. 

It is featured in the Toolbox column where they highlight useful tools and blogs. Here is a snippet of what it says:

Creating Code Snippets is a lot easier when using Snippet Designer (version 1.1), a free, open-source Add-In for Visual Studio 2008 for creating and editing Code Snippets directly within the IDE. Once you install it, creating a new Code Snippet is as easy as going to the File menu and creating a new Code Snippet File.

That is so cool! If you are interested go and download the Snippet Designer from the Codeplex website and give me more feedback.

Also, in the same article my friend Sara Ford had her blog featured.  When I found out the Snippet Designer and Sara’s blog were in the magazine I quickly emailed to ask Sara if she knew about it.  She already did and also had an extra copy of the magazine for me!