Tag: C#/.Net

Brant Estes of Magenic Technologies has just posted a very nice online quiz for .Net programmers. The test is there to pre-screen potential candidates to work at Magenic, but it’s also a very nice test for any .Net programmer to take (or to give to any .Net programmer you have considered hiring).

I took the test and scored a 75 out of 100 (without cheating, mind you), and was told I may make a great addition to Magenic. Unfortunately, I live in New York, and I’m not relocating. Besides, I just put in my resignation with my current employer so I can go back to independent consulting, so I’m not exactly on the market for full-time employment… but more on that another day.

I’ve been using Phil Haack‘s Custom Configuration Sections in 3 Easy Steps for some time now, and my configuration file management has never been happier… until I needed to read a collection of configuration elements.

Here’s a sample of the XML I needed to incorporate:

<importer>
	<filespecs>
		<add type="EmployeeCSV" path="d:\import\employees.csv" />
		<add type="OrderCSV" path="d:\import\orders_*.csv" />
	</filespecs>   
</importer>

The typical solution is to write your own collection class (FilespecConfigurationElementCollection), inheriting from ConfigurationElementCollection, and ensuring your Filespec object inherits from ConfigurationElement. I figured there has to be a better way — and there is.

I wrote a generic version of ConfigurationElementCollection, which you can use to avoid writing the custom collection class. The code that follows is the generic class, the Filespec object I used, and the property declaration from my ConfigurationSettings class (as described in Phil’s previously mentioned article).

Note one key part of this implementation: You must override the ToString() method of your custom ConfigurationElement class to return a unique value. The generic ConfigurationElementCollection uses the ToString() method to obtain a unique key for each element in the collection.

// The ConfigurationElementCollection<t> provides a simple generic implementation of ConfigurationElementCollection.
[ConfigurationCollection(typeof(ConfigurationElement))]
public class ConfigurationElementCollection</t><t> : ConfigurationElementCollection where T : ConfigurationElement, new()
{
	protected override ConfigurationElement CreateNewElement()
	{
		return new T();
	}
	protected override object GetElementKey(ConfigurationElement element)
	{
		return ((T)(element)).ToString();
	}
	public T this[int idx]
	{
		get { return (T)BaseGet(idx); }
	}
}
// The Filespec class is an example of a custom configuration element.
// Note that we inherit from ConfigurationElement, and use ConfigurationProperty attributes.
public class Filespec : ConfigurationElement
{
	public Filespec()
	{
	}
	[ConfigurationProperty("path", DefaultValue="", IsKey=true, IsRequired=true)]
	public string Path
	{
		get { return (string)(base["path"]); }
		set { base["path"] = value; }
	}
	[ConfigurationProperty("type", IsKey=false, IsRequired = true)]
	public FilespecType Type
	{
		get { return (FilespecType)(base["type"]); }
		set { base["type"] = value; }
	}

	public override string ToString()
	{
		return this.Path;
	}
}
// Finally, our ConfigurationSettings class (only part of the class is included).
// Note how we use the generic ConfigurationElementCollection.
public class ConfigurationSettings : ConfigurationSection
{
// ...
	[ConfigurationProperty("filespecs", IsRequired=true)]
	public ConfigurationElementCollection<filespec> FileSpecs
	{
		get { return (ConfigurationElementCollection</filespec><filespec>)this["filespecs"]; }
	}
// ...
}

If you’re using a number of ConfigurationElementCollections, this is a great way to simplify your code.

I received word that my third article for .Net Developer’s Journal will appear in the September 2004 issue. It’s the third in the series of articles entitled, “C# and the .Net Framework: Tying It All Together”. The first article was in the January 2004 issue, the second article was in the May 2004 issue. Why such a delay between articles? They never told me they were publishing the first article, so I didn’t get the second article to them until after it printed. They never received the third article (which was originally sent in May 2004) and we didn’t catch up with each other until last month. I’m working on the fourth article now and hopefully it’ll be in the October or November issue.

My latest article, C# and the .Net Framework: Tying It All Together (Part 2) has been published in the May 2004 issue of the .Net Developer’s Journal. Check it out, and let me know what you think!