读取ConfigurationSection

Question

I'm writing a Windows service that needs some information from the app.config - I know I could use AppSettings , but I'm trying to understand config sections a little better.

I've modified my App.Config:

<configuration>
  <startup>
    <supportedRuntime sku=".NETFramework,Version=v4.0"
                      version="v4.0"/>
  </startup>

  <configSections>
    <section name="config"
             type="MyNamespace.MyConfigurationSection"/>
  </configSections>

  <config aNumber="1"
          aBoolean="false"/>

</configuration>

and created the following class:

public sealed class MyConfigurationSection : ConfigurationSection
{
    [ConfigurationProperty("aNumber", DefaultValue = 1, IsRequired = false)]
    public int Number
    {
        get { return (int) this["aNumber"]; }
        set { this["aNumber"] = value; }
    }

    [ConfigurationProperty("aBoolean", DefaultValue = false, IsRequired = false)]
    public bool Boolean
    {
        get { return (bool) this["aBoolean"]; }
        set { this["aBoolean"] = value; }
    }
}

and I'm trying to access it like this:

public MyConfigurationSection ConfigSection
{
    get
    {
        var configurationSection = Configuration.GetSection("config");
        return (MyConfigurationSection) configurationSection;
    }
}

private static Configuration Configuration
{
    get { return ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None); }
}

Everything works fine until I get to the (MyConfigurationSection) configurationSection cast. I'm getting back a DefaultSection from my call to GetSection() , and the cast fails.

Where have I gone astray?

Answer 1

Possibly, although didn't check,

type="MyNamespace.MyConfigurationSection"/>

Should be

type="<Namespace.ClassName>,<Namespace>"/>

Answer 2

The catch here is, you have to use the type value as "Namespace.ClassName, Namespace" in section configuration in app.config and more importantly the configSections must be the first child of the root configuration element in your app.config

Below configuration might work for you:

<configuration>
      <!-- <configSections> is moved to first child of <configuration> -->
      <configSections>
        <section name="config"
                 type="MyNamespace.MyConfigurationSection, MyNamespace"/>
      </configSections>

      <config aNumber="1"
              aBoolean="false"/>

      <startup>
        <supportedRuntime sku=".NETFramework,Version=v4.0"
                          version="v4.0"/>
      </startup>
</configuration>

Answer 3

config is a reserved word and cannot be used for the name of a configuration section. You also shouldn't name a variable Boolean.

Try this following example:

using System.Configuration;

namespace ConfigSectionSample
{
    internal class MyConfigurationSection : ConfigurationSection
    {
        public static MyConfigurationSection Current
        {
            get
            {
                return (MyConfigurationSection)ConfigurationManager.GetSection("myConfig");
            }
        }

        [ConfigurationProperty("aNumber", IsRequired = true)]
        public int Number
        {
            get
            {
                return (int)this["aNumber"];
            }
        }

        [ConfigurationProperty("aBoolean", IsRequired = true)]
        public bool Boolean
        {
            get
            {
                return (bool)this["aBoolean"];
            }
        }
    }
}

With the following app,config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="myConfig" type="ConfigSectionSample.MyConfigurationSection, ConfigSectionSample"></section>
  </configSections>

  <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
    </startup>

  <myConfig aNumber="1" aBoolean="false" />
</configuration>

And get the values like this:

        Console.WriteLine("Number: " + MyConfigurationSection.Current.Number);
        Console.WriteLine("Boolean: " + MyConfigurationSection.Current.Boolean);
        Console.ReadLine();