ConfigurationManager立即给出TypeInitializationException

我正在制作一个需要读取其配置文件以获取设置的应用程序。

我在App_config文件中定义了如下设置：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="sswcomm" type="SSWAgent.SSWConfig" />
    <section name="folders" type="SSWAgent.SSWConfigFolderCollection" />
    <section name="folder" type="SSWAgent.SSWConfigFolderElement" />
  </configSections>
  <sswcomm id="SC_SSWTEST1" connectionInterval="5000">
    <folders>
      <folder id="OUTGOINGATOTEST2" enable="true" includeSubFolders="true" fromPath="C:'temp'a'NET'Outgoing_A" wildcard="*.*" recipientId="C_SSWTEST2" />
      <folder id="OUTGOINGBTOTEST3" enable="true" includeSubFolders="true" fromPath="C:'temp'a'NET'Outgoing_B" wildcard="*.*" recipientId="C_SSWTEST3" />
    </folders>
  </sswcomm>
</configuration>

C#代码是这样的：

public sealed class SSWConfig : ConfigurationSection
    {
        private static SSWConfig settings = ConfigurationManager.GetSection("sswcomm") as SSWConfig;
        public static SSWConfig Settings
        {
            get { return settings; }
        }
        [ConfigurationProperty("id", DefaultValue = "", IsKey = true, IsRequired = true)]
        [StringValidator(InvalidCharacters = "  ~!@#$%^&*()[]{}/;’'"|''", MinLength = 1, MaxLength = 256)]
        public string Id
        {
            get { return (string)this["id"]; }
            set { this["id"] = value; }
        }
        [ConfigurationProperty("connectionInterval", DefaultValue = "", IsKey = true, IsRequired = true)]
        public int ConnectionInterval
        {
            get { return (int)this["connectionInterval"]; }
            set { this["connectionInterval"] = value; }
        }
        [ConfigurationProperty("folders", IsDefaultCollection = true, IsKey = false, IsRequired = true)]
        public SSWConfigFolderCollection Folders
        {
            get { return base["folders"] as SSWConfigFolderCollection; }
        }
    }
    public sealed class SSWConfigFolderCollection : ConfigurationElementCollection
    {
        protected override ConfigurationElement CreateNewElement()
        {
            return new SSWConfigFolderElement();
        }
        protected override object GetElementKey(ConfigurationElement element)
        {
            return ((SSWConfigFolderElement)element).Id;
        }
        new public SSWConfigFolderElement this[string Id]
        {
            get { return (SSWConfigFolderElement)base.BaseGet(Id); }
        }
        public override ConfigurationElementCollectionType CollectionType
        {
            get
            {
                return ConfigurationElementCollectionType.BasicMap;
            }
        }
        public SSWConfigFolderElement this[int index]
        {
            get { return (SSWConfigFolderElement)base.BaseGet(index); }
        }
        protected override string ElementName
        {
            get
            {
                return "folder";
            }
        }
    }
    public sealed class SSWConfigFolderElement : ConfigurationElement
    {
        [ConfigurationProperty("id", DefaultValue = "", IsKey = true, IsRequired = true)]
        [StringValidator(InvalidCharacters = "  ~!@#$%^&*()[]{}/;’'"|''", MinLength = 1, MaxLength = 256)]
        public string Id
        {
            get { return (string)base["id"]; }
            set { base["id"] = value; }
        }
        [ConfigurationProperty("enable", DefaultValue = "true", IsKey = false, IsRequired = true)]
        public bool Enable
        {
            get { return (string)base["enable"] == "true"; }
            set { if (value) { base["enable"] = "true"; } else { base["enable"] = "false"; } }
        }
        [ConfigurationProperty("includeSubFolders", DefaultValue = "true", IsKey = false, IsRequired = true)]
        public bool IncludeSubFolders
        {
            get { return (string)base["includeSubFolders"] == "true"; }
            set { if (value) { base["includeSubFolders"] = "true"; } else { base["enable"] = "false"; } }
        }
        [ConfigurationProperty("fromPath", DefaultValue = "", IsKey = false, IsRequired = true)]
        public string FromPath
        {
            get { return (string)base["fromPath"]; }
            set { base["fromPath"] = value; }
        }
        [ConfigurationProperty("wildcard", DefaultValue = "*.*", IsKey = false, IsRequired = true)]
        public string Wildcard
        {
            get { return (string)base["wildcard"]; }
            set { base["wildcard"] = value; }
        }
        [ConfigurationProperty("recipientId", DefaultValue = "", IsKey = false, IsRequired = true)]
        [StringValidator(InvalidCharacters = "  ~!@#$%^&*()[]{}/;’'"|''", MinLength = 1, MaxLength = 256)]
        public string RecipientId
        {
            get { return (string)base["recipientId"]; }
            set { base["recipientId"] = value; }
        }
    }

现在，每当我调用SSWConfig并将其放入变量中时，我都会立即得到一个TypeInitializationException异常。我认为是因为GetSection部分返回null。这是因为我在App.config文件中犯了一个错误吗？

带有嵌套元素的app.config对我来说是新的，所以可能是我定义错了。