JavaScript enums

[This was originally posted at http://timstall.dotnetdevelopersjournal.com/javascript_enums.htm]

While JavaScript does not explicitly have the enum keyword, you can work around it using JS rich objects to get the functional equivalent. Here's a minimalist example that defines the enum, passes it in as a parameter, and then checks for it in a switch-case statement. Although, this doesn't throw a "compile time" exception if you pass in an invalid value.

    var Enum_Colors =
    {
      Red:0,
      Blue:1,
      Green:2,
      Yellow:3
    };
   
    function DoStuff()
    {
      TestEnum(Enum_Colors.Green);
    }

    function DoError()
    {
      TestEnum(Enum_Colors.Unknown); //Bad
    }
    function TestEnum(objColorEnum)
    {
      var str;
      switch(objColorEnum)
      {
        case Enum_Colors.Red:
          str = "red";
          break;
        case Enum_Colors.Blue:
          str = "blue";
          break;
        case Enum_Colors.Green:
          str = "green";
          break;
        case Enum_Colors.Yellow:
          str = "yellow";
          break;
        default:
          str = "none";
          break;
      }
     
      alert("The enum passed in is: " + str);
    }

 Thanks to VS2008, you at least get JS intellisence on the "Enum_Colors" object, so that's better than just typing in error-prone literal strings.

Convert from a MemoryStream to a string and back

[This was originally posted at http://timstall.dotnetdevelopersjournal.com/convert_from_a_memorystream_to_a_string_and_back.htm]

A stream in .Net is a sequence of bytes. There are several types of streams. A common one is the MemoryStream which uses memory for its storage (as opposed to a file system, or something else). Several readers and writers require a stream as an input parameter, and you'll find that sometimes you'll just want to be able to easily convert from a string to a MemoryStream and back. Here are two easy utility methods to do that:

    public static string GetStringFromMemoryStream(MemoryStream m)
    {
      if (m == null || m.Length == 0)
        return null;

      m.Flush();
      m.Position = 0;
      StreamReader sr = new StreamReader(m);
      string s = sr.ReadToEnd();

      return s;
    }

    public static MemoryStream GetMemoryStreamFromString(string s)
    {
      if (s == null || s.Length == 0)
        return null;

      MemoryStream m = new MemoryStream();
      StreamWriter sw = new StreamWriter(m);
      sw.Write(s);
      sw.Flush();

      return m;
    }

 

We can easily test these with a round-trip method. Note that ideally we'd have one test for each specific method, but this is just for demo purposes:

 

    [TestMethod]
    public void Convert_RoundTrip()
    {
      string s1 = "Hello World!";
      MemoryStream m = GetMemoryStreamFromString(s1);

      Assert.AreEqual(12, m.Length);

      string s2 = GetStringFromMemoryStream(m);

      Assert.AreEqual(s1, s2);
    }

 

 

My Startup Script

[This was originally posted at http://timstall.dotnetdevelopersjournal.com/my_startup_script.htm]

 

I don't like re-starting my machine because I need to re-open all the misc windows and files I have loaded. However, because I still need to reboot, I wrote a simple script to open common programs and files for me.

REM: Open Windows Explorer

start explorer
start explorer

REM: Open NotePad

start notepad
start notepad "C:\MyDocuments\temp.txt"

REM: Open the DOS command window, default to a certain folder

start cmd "/Kcd C:\Utils\MyTasks"

REM: Open Internet Explorer

start /B /D"C:\Program Files\Internet Explorer" iexplore.exe

REM: Open a Visual Studio solution

start /B /D"C:\MySolutions\StandardFiles" StandardFiles.sln

This opens five main things:

• Windows Explorer

• Notepad - a blank version, and one that stores a simple scratchpad of notes. You could also open other scratchpads.

• Internet Explorer (could just as easily be firefox). There are also ways to pre-populate the tabs.

• Cmd window - I set it to a directory that has a bunch of misc scripts (using the "/K" switch to call the CD command)

• Visual Studio - In this case I open a solution folder with a bunch of misc xml files that I use.

Of course you can add other programs to the list too.

 

Lastly, I made a shortcut of this batch script on my desktop, so I just click it when Windows loads up. (You could probably automate the startup tasks if you want).

Silverlight Xaml error: "Length cannot be less than zero. Parameter name: length"

[This was originally posted at http://timstall.dotnetdevelopersjournal.com/silverlight_xaml_error_length_cannot_be_less_than_zero_pa.htm]

I was getting a strange Silverlight compile error in my Page.xaml the other day (while migrating stuff from 1.1 Alpha to 2.0 Beta):

Length cannot be less than zero.
Parameter name: length

At first it sounds like I was setting a wrong value - like trying to reference the "-1" position on a string. But, it actually was a constraint in what namespaces Xaml allows.

 

In 1.1 Alpha, this would be ok:

xmlns:Tank.Core="clr-namespace:Tank.Core;assembly=Tank.Core"

Which you could then reference like so:

However, that line kept throwing the error when I tried to compile.

 

It seems like if I remove the period ".", then it works again, like so:

xmlns:Tank1="clr-namespace:Tank.Core;assembly=Tank.Core"

Strange. I'm not fully sure why, maybe some parsing thing with periods "." in beta, but it was good to have a work-around.

Excuses for installing a game on your work laptop

[This was originally posted at http://timstall.dotnetdevelopersjournal.com/excuses_for_installing_a_game_on_your_work_laptop.htm]

Of course work laptops are for work, and should only be used for "company purposes". So, how do some people justify installing games on their work machines:

• "It's part of the operating system - Windows won't run unless I install these games. Really."

• "By installing on my main work laptop, I'm using that laptop more, so I'm more familiar with how it works and I can more easily check work-related tasks (like email and IM, and things that require the VPN)."

• "These games have technical educational value, and are therefore not really 'games', but rather learning tutorials that benefit the company."

• "I'm not 'playing the game', I'm studying it to better understand how to make functional user interfaces."

• "I'm just analyzing the deployment experience so I can glean from it and apply it to our own product."

• "This isn't really a game, it's actually a test project that I wrote myself (such as with XNA or Silverlight)."

• "This game was built by one of our clients, so I'm just studying their products to help me conduct better client outreach."

I'm sure there's more.