读取app.config配置的相关问题

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近用到需要在App.config 文件中配置相关内容的代码，遇到过一些问题，总结了一下：

首先如果配置文件中有 configSections 节点，该节点必须放在第一位否则会出现各种问题。
自定义的配置必须在 configSections 节点中进行声明，否则读取相关Section信息的时候返回值为null。
如下给出一段在 App.config 文件中自定义配置的代码：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
<appSettings>
<add key="loginUrl" value="~/RedirectValue.cshtml" />
<add key="autoFormsAuthentication" value="false"/>
</appSettings>
<configSections>
<!-- Servcies Defination -->
<section name="services" type="ServciesHost.ServicesConfig, ServciesHost"/>
</configSections>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2"/>
</startup>
<services>
<confs>
<service id="0001" name="TestService1" path="TestService1.exe" description="TestService1"/>
<service id="0002" name="TestService2" path="TestService2.exe" description="TestService2"/>
</confs>
</services>
</configuration>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;

namespace ServciesHost
{
public class ServiceElement:ConfigurationElement
{
[ConfigurationProperty("id")]
public string Id
{
get { return (string)this["id"]; }
set { this["id"] = value; }
}

[ConfigurationProperty("name")]
public string Name
{
get { return (string)this["name"]; }
set { this["name"] = value; }
}

[ConfigurationProperty("path")]
public string Path
{
get { return (string)this["path"]; }
set { this["path"] = value; }
}

[ConfigurationProperty("description")]
public string Description
{
get { return (string)this["description"]; }
set { this["description"] = value; }
}
}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;

namespace ServciesHost
{
public class ServcieCollection:ConfigurationElementCollection
{

public ServiceElement this[int index]
{
get { return (ServiceElement)BaseGet(index); }
}

public new ServiceElement this[string id]
{
get { return (ServiceElement)BaseGet(id); }
}

protected override ConfigurationElement CreateNewElement()
{
return new ServiceElement();
}

protected override object GetElementKey(ConfigurationElement element)
{
return ((ServiceElement)element).Id;
}
}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;
using System.IO;
using System.Reflection;

namespace ServciesHost
{
public class ServicesConfig:ConfigurationSection
{
private static ServicesConfig _servicesConfig = null;

[ConfigurationProperty("confs", IsDefaultCollection = true)]
[ConfigurationCollection(typeof(ServcieCollection), AddItemName = "service")]
public ServcieCollection Services
{
get { return (ServcieCollection)this["confs"]; }
}

public static ServicesConfig CurrentConfig
{
get {
return _servicesConfig;
}
}

private static Configuration _config;

public static ServicesConfig Initialize()
{
try
{
_config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
_servicesConfig = _config.GetSection("services") as ServicesConfig;

}
catch (Exception ex)
{
throw ex;
}

return _servicesConfig;
}
}

public class NameValueSection : ConfigurationSection
{
[ConfigurationProperty("", IsDefaultCollection = true)]
public NameValueConfigurationCollection Settings
{
get
{
return (NameValueConfigurationCollection)base[""];
}
}
}
}

using CommonLibary;
using System.Configuration;
using System;

namespace ServciesHost
{
class Program
{
static void Main(string[] args)
{
ServicesConfig.Initialize();
Console.ReadLine();
}
}
}