March « 2010 « Justin DuJardin

28
Mar/100

Custom Metadata tags in C# code

Some dynamic languages like C# and ActionScript allow you to put metadata inline with your code. Metadata can be a really cool way to make extra data available to you at runtime. To make full use of it, you need to know how to specify this metadata and then how to access it.

MetadataSample.cs

The sample below shows how to specify a custom Attribute called “SomeExtraData”, use it on a class “SomeClass” and retrieve the custom data in code for further use.

using System;
using System.Diagnostics;

namespace SilverShorts
{
   // This class makes the [SomeExtraData] tag below valid
   class SomeExtraData : Attribute
   {
      public string SomeField;
   }

   // Tag this class with a custom attribute
   [SomeExtraData (SomeField="SomeValue")]
   class SomeClass
   {
      public SomeClass()
      {
         // Retrieve the value of the SomeField item in the metadata
         // tag on this class.
         Type t = typeof(SomeClass);
         SomeExtraData attr = t.GetCustomAttributes(false)[0] as SomeExtraData;
         Debug.WriteLine("SomeExtraData.SomeField = " + attr.SomeField);
      }
   }
}

A word of caution: Be aware of how often you perform operations like querying custom attributes in the constructor above. The system reflection calls can negatively impact performance if you abuse them. I won’t preach about it, just use them only when you need to.

Tagged as: Attribute, C#, Metadata

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9
Mar/100

Silverlight 3, LINQ, and Bing! Oh, my!

In my last post I talked about Silver Shorts and showed off my example Bing Image search application.

For this post I want to go over the code that I created for doing a Bing image query, to demonstrate just how powerful and concise Silverlight 3 C# code can be. To truly appreciate this, I suggest checking out the code, which totals about 225 lines for both the Image Search utility AND the Test Application.

To get started, let’s enumerate the requirements I came up with for the project:

Image Search
- Bing Image query based on textual search terms
- Transform XML results into custom classes

We’ll refer back to these requirements as we build the code to make sure we stay on track.

Tagged as: Bing, Image Query, Linq to Xml, Silverlight 3

6
Mar/100

Project Silver Shorts

Last week I decided to install the Visual Studio 2010 RC for the purposes of messing around with C#, Silverlight 3, and all the new WPF goodness that came with it. I only intended to dabble for a day or so, but ended up having my entire week consumed in what seemed like a moment.

If you have Silverlight installed, you can view the end result of my first experiment after the page break. It is a simple Bing image searcher that displays thumbnails of the results on a canvas.

What is Project Silver Shorts?

More than anything Silver Shorts is an idea, a codename for a collection of demos in C#, most of which have yet to be written, targeting Silverlight 3, that are intended to be Short. As I stumble and bumble my way around .NET, finding new and interesting things to do with it, I will make my experiments available with full source code on GitHub (skip to the bottom if all you care about is code.)

For the developers in the audience, let’s take a look at a simple LINQ query I have fabricated to summarize the goals of Silver Shorts while simultaneously showing off how neat LINQ is.

var blogPosts =
   from exp in user.Experiences()
   where exp.IsAwesome
   select new BlogPost()
   {
      Title = exp.Concept,
      Content = exp.Details,
      CodeUrl = exp.GitUrl;
   };

To be painfully and obnoxiously clear, this code example is not part of the actual demo program, it is only here to look pretty and be a conversation piece.

Filed under: C#, Development, Silverlight

Justin DuJardin |O_o| |x_X| |-_-| |o_O|

Custom Metadata tags in C# code

Silverlight 3, LINQ, and Bing! Oh, my!

Project Silver Shorts

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