如何在自定义configSection中指定集合

Question

我想有一个xml配置文件,如下所示:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
    <section name="plugins" type="MyApp.PluginsConfiguration, MyApp"/>
</configSections>

<plugins>
    <use assembly="MyApp.Plugin1.dll" />
    <use assembly="MyApp.Plugin2.dll" />
</plugins>
</configuration>

我如何安排我的代码中的PluginsConfigurations,UsePluginCollection和UsePlugin类之间的相互作用？

我在网上找到了这个教程,但它会在插件中引入一个围绕使用集合的元素,我不需要这个.

这是我到目前为止所做的,但不太正确

Answer 1

如果MyApp.PluginsConfiguration是ConfigurationSection,那么您可以定义一个继承自ConfigurationElementCollection的新类,并使新类成为MyApp.PluginsConfiguration的ConfigurationProperty.

查看本文以获取有关这些类型的一些深入信息.我还写了关于嵌套属性的博客,但没有专门针对集合.

编辑:这里有一些代码.鉴于web.config中的这一点:

<configSections>
    <section name="plugins"
             type="WebApplication1.PluginsConfiguration, WebApplication1"/>
</configSections>
<plugins>
    <use assembly="MyApp.Plugin1.dll"/>
    <use assembly="MyApp.Plugin2.dll"/>
</plugins>

这是实现这一目标的类.请注意,可能需要处理NullReferenceExceptions.

namespace WebApplication1
{
    public class PluginsConfiguration : ConfigurationSection
    {
        private static ConfigurationPropertyCollection properties;
        private static ConfigurationProperty propPlugins;

        static PluginsConfiguration()
        {
            propPlugins = new ConfigurationProperty(null, typeof(PluginsElementCollection),
                                                          null,
                                                          ConfigurationPropertyOptions.IsDefaultCollection);
            properties = new ConfigurationPropertyCollection { propPlugins };
        }

        protected override ConfigurationPropertyCollection Properties
        {
            get
            {
                return properties;
            }
        }

        public PluginsElementCollection Plugins
        {
            get
            {
                return this[propPlugins] as PluginsElementCollection;
            }
        }
    }

    public class PluginsElementCollection : ConfigurationElementCollection
    {
        public PluginsElementCollection()
        {
            properties = new ConfigurationPropertyCollection();
        }

        private static ConfigurationPropertyCollection properties;

        protected override ConfigurationPropertyCollection Properties
        {
            get
            {
                return properties;
            }
        }

        public override ConfigurationElementCollectionType CollectionType
        {
            get
            {
                return ConfigurationElementCollectionType.BasicMap;
            }
        }

        protected override string ElementName
        {
            get
            {
                return "use";
            }
        }

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

        protected override object GetElementKey(ConfigurationElement element)
        {
            var elm = element as PluginsElement;
            if (elm == null) throw new ArgumentNullException();
            return elm.AssemblyName;
        }
    }

    public class PluginsElement : ConfigurationElement
    {
        private static ConfigurationPropertyCollection properties;
        private static ConfigurationProperty propAssembly;

        protected override ConfigurationPropertyCollection Properties
        {
            get
            {
                return properties;
            }
        }

        public PluginsElement()
        {
            propAssembly = new ConfigurationProperty("assembly", typeof(string),
                                                          null,
                                                          ConfigurationPropertyOptions.IsKey);
            properties = new ConfigurationPropertyCollection { propAssembly };
        }

        public PluginsElement(string assemblyName)
            : this()
        {
            AssemblyName = assemblyName;
        }

        public string AssemblyName
        {
            get
            {
                return this[propAssembly] as string;
            }
            set
            {
                this[propAssembly] = value;
            }
        }
    }
}

要访问它,此代码段应该有所帮助:

        var cfg = WebConfigurationManager.GetWebApplicationSection("plugins") as PluginsConfiguration;
        var sb = new StringBuilder();
        foreach(PluginsElement elem in cfg.Plugins)
        {
            sb.AppendFormat("{0}<br/>", elem.AssemblyName);
        }
        testLabel.Text = sb.ToString();

基本上我们有一个处理plugins-element的ConfigurationSection.在这里,我们指定一个ConfigurationElementCollection属性并将其声明为默认集合(理论上你可以在一个根节点下有多个不同的集合).

PluginsElementCollection实现ConfigurationElementCollection.ElementName必须是标记的名称,在我们的例子中是"use".此外,需要重写GetElementKey,并且应返回条目中唯一的属性.

然后,PluginsElement实现单个use标记.我们只定义一个属性:AssemblyName,它映射到assembly-attribute.

我没有声称完全理解所有这些(特别是ConfigurationElementCollection和它的各种BaseAdd,BaseGet等属性在这里没有真正探索过),但我可以声称这有效:)

此外,它不使用任何属性.我讨厌属性 - 幸运的是,所有这些属性都可以转换为正确的代码.您可以使用其中一个(或两个).