Why does ConfigurationSection need to look things up with a string?

Question

The ConfigurationSection examples I have found online (for example) all have code that looks like this:

public class ConnectionSection  : ConfigurationSection
{
    [ConfigurationProperty("Servers")]
    public ServerAppearanceCollection ServerElement
    {
        get { return ((ServerAppearanceCollection)(base["Servers"])); }
        set { base["Servers"] = value; }
    }
}

Why is it accessing the value "Servers" from the base using the square brackets? Is the setter used when creating this object from the xml, or is the setter used to overwrite the value in the xml file? If so, why is the attribute set on this property?

CodeCaster · Accepted Answer · 2015-09-04T11:03:03.820

8

Why is it accessing the value "Servers" from the base using the square brackets?

Because the base class, ConfigurationSection, doesn't know what properties its inheritors are going to implement.

So it exposes a string indexer: this[string] which lets you access the values read from the configuration.

This was a design decision. The .NET team could also have opted to use reflection to get and set the inheritor's properties, but decided not to. (Well, of course there's lots of reflection going in in configuration sections, but not up till the point that public ServerAppearanceCollection ServerElement { get; set; } would work).

edited Sep 04 '15 at 11:03

answered Sep 04 '15 at 10:50

CodeCaster

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ok, so the setter isn't really needed if I'm only using ReadOnly config files? – Marius Sep 04 '15 at 10:52
@Marius I just tried it, and the setter is optional. – CodeCaster Sep 04 '15 at 11:03

score 3 · Answer 2 · answered Sep 04 '15 at 11:00

3

A little addition to @CodeCaster's answer.
With C#6 you can make your life a bit easier:

class MyConfigSection : ConfigurationSection
{
    [ConfigurationProperty(nameof(SomeProperty))]
    public int SomeProperty
    {
        get { return ((int)(base[nameof(SomeProperty)])); }
        set { base[nameof(SomeProperty)] = value; }
    }
}

especially, if this code block will be turned into code snippet.

answered Sep 04 '15 at 11:00

Dennis

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Cool, that at least makes it a bit cleaner – Marius Sep 04 '15 at 13:07

Why does ConfigurationSection need to look things up with a string?

2 Answers2