本文主要介紹自己在使用Unity時碰到的一個問題，及解決方案。
由于本人不擅長寫作，所以文字都很簡單，各位還是主要看代碼及DEMO吧。

首先先看一下以下代碼：

????public?interface?ILogger
????{
????????void?Write();
????}

????public?class?FlatFileLogger?:?ILogger
????{
????????private?Message?_message;
????????public?FlatFileLogger(Message?message)
????????{
????????????_message?=?message;
????????}

????????public?void?Write()
????????{
????????????Console.WriteLine(String.Format("Message:{0}",?_message));
????????????Console.WriteLine("Target:FlatFile");
????????}
????}

????public?class?Message
????{
????????private?string?_message;
????????private?Message(string?message)
????????{
????????????_message?=?message;
????????}

????????public?override?string?ToString()
????????{
????????????return?_message.ToString();
????????}

????????public?static?Message?CreateMessage(string?message)
????????{
????????????return?new?Message(message);
????????}
????}

????class?Program
????{
????????static?void?Main(string[]?args)
????????{
????????????IUnityContainer?container?=?new?UnityContainer();
????????????UnityConfigurationSection?section?=?(UnityConfigurationSection)ConfigurationManager.GetSection("unity");
????????????section.Containers["containerOne"].Configure(container);

????????????ILogger?log?=?container.Resolve<ILogger>();
????????????log.Write();

????????????Console.ReadLine();
????????}
????}
配置文件：

<?xml?version="1.0"?encoding="utf-8"??>
<configuration>
????<configSections>
????????<section?name="unity"?type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection,
?????????????????Microsoft.Practices.Unity.Configuration,?Version=1.0.0.0,
?????????????????Culture=neutral,?PublicKeyToken=31bf3856ad364e35"?/>
????</configSections>
????<unity>
????????<typeAliases>
????????????<typeAlias?alias="string"?type="System.String,?mscorlib"?/>

????????????<!--?Lifetime?manager?types?-->
????????????<typeAlias?alias="singleton"
?????????????????type="Microsoft.Practices.Unity.ContainerControlledLifetimeManager,
???????????????Microsoft.Practices.Unity"?/>
????????????<typeAlias?alias="external"
?????????????????type="Microsoft.Practices.Unity.ExternallyControlledLifetimeManager,
???????????????Microsoft.Practices.Unity"?/>

????????????<!--?User-defined?type?aliases?-->
????????????<typeAlias?alias="ILogger"?type="UnityDemo.ILogger,?UnityDemo"?/>
????????????<typeAlias?alias="FlatFileLogger"?type="UnityDemo.FlatFileLogger,?UnityDemo"?/>
????????????<typeAlias?alias="Message"?type="UnityDemo.Message,?UnityDemo"?/>
????????</typeAliases>
????????<containers>
????????????<container?name="containerOne">
????????????????<types>
?????????????????????<type?type="ILogger"?mapTo="FlatFileLogger"/>
????????????????</types>
????????????</container>
????????</containers>
????</unity>
</configuration>
一運行程序就報錯，那是因為Message類的構造函數是私有的，Unity無法自動裝配。

本來父對象的構造函數如果需要指定具體值，可以通過修改配置文件來達到目的，配置修改如下：

<type?type="ILogger"?mapTo="FlatFileLogger">
????????????????????????<typeConfig?extensionType="Microsoft.Practices.Unity.Configuration.TypeInjectionElement,
?????????????????????????????????????Microsoft.Practices.Unity.Configuration">
????????????????????????????<constructor>
????????????????????????????????<param?name="message"?parameterType="Message">
????????????????????????????????????<value?value="Some?Value"></value>
????????????????????????????????</param>
????????????????????????????</constructor>
????????????????????????</typeConfig>
????????????????????</type>
但現在還有一個問題，就是由于參數message的類型是自定義類型，不是像string, int等系統類型， 按以上配置是無法把一個Message的實例傳給FlatFileLogger的構造函數的。這時就需要用到typeConverter，把value中的值轉換成一個Message的實例。

LoggerConverter：

???public?class?LoggerConverter?:?TypeConverter
????{
????????public?override?bool?CanConvertFrom(ITypeDescriptorContext?context,?Type?sourceType)
????????{
????????????if?(sourceType?==?typeof(string))
????????????{
????????????????return?true;
????????????}
????????????return?base.CanConvertFrom(context,?sourceType);
????????}

????????public?override?object?ConvertFrom(ITypeDescriptorContext?context,
???????????CultureInfo?culture,?object?value)
????????{
????????????if?(value?is?string)
????????????{
????????????????return?Message.CreateMessage(value.ToString());
????????????}
????????????return?base.ConvertFrom(context,?culture,?value);
????????}
????}

?修改后最終的配置文件：

<?xml?version="1.0"?encoding="utf-8"??>
<configuration>
????<configSections>
????????<section?name="unity"?type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection,
?????????????????Microsoft.Practices.Unity.Configuration,?Version=1.0.0.0,
?????????????????Culture=neutral,?PublicKeyToken=31bf3856ad364e35"?/>
????</configSections>
????<unity>
????????<typeAliases>
????????????<typeAlias?alias="string"?type="System.String,?mscorlib"?/>

????????????<!--?Lifetime?manager?types?-->
????????????<typeAlias?alias="singleton"
?????????????????type="Microsoft.Practices.Unity.ContainerControlledLifetimeManager,
???????????????Microsoft.Practices.Unity"?/>
????????????<typeAlias?alias="external"
?????????????????type="Microsoft.Practices.Unity.ExternallyControlledLifetimeManager,
???????????????Microsoft.Practices.Unity"?/>

????????????<!--?User-defined?type?aliases?-->
????????????<typeAlias?alias="ILogger"?type="UnityDemo.ILogger,?UnityDemo"?/>
????????????<typeAlias?alias="FlatFileLogger"?type="UnityDemo.FlatFileLogger,?UnityDemo"?/>
????????????<typeAlias?alias="LoggerConverter"?type="UnityDemo.LoggerConverter,?UnityDemo"?/>
????????????<typeAlias?alias="Message"?type="UnityDemo.Message,?UnityDemo"?/>
????????</typeAliases>
????????<containers>
????????????<container?name="containerOne">
????????????????<types>
?????????????????????<type?type="ILogger"?mapTo="FlatFileLogger"?name="FlatFileLogger"?/>
?????????????????????<type?type="ILogger"?mapTo="DatabaseLogger"?name="DatabaseLogger"/>
?????????????????????
?????????????????????<type?type="ILogger"?mapTo="FlatFileLogger">
????????????????????????<typeConfig?extensionType="Microsoft.Practices.Unity.Configuration.TypeInjectionElement,
?????????????????????????????????????Microsoft.Practices.Unity.Configuration">
????????????????????????????<constructor>
????????????????????????????????<param?name="message"?parameterType="Message">
????????????????????????????????????<value?value="FlatFileLogger"?type="Message"?typeConverter="LoggerConverter"></value>
????????????????????????????????</param>
????????????????????????????</constructor>
????????????????????????</typeConfig>
????????????????????</type>
????????????????????
????????????????</types>
????????????</container>
????????</containers>
????</unity>
</configuration>
經過修改后，程序終于可以正常運行了。
運行結果：
?

本文代碼

轉載于:https://www.cnblogs.com/NickYao/archive/2008/05/04/1181804.html

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