Unity中使用多构造函数

如果要实例化的类只有一个构造函数, 则使用方法很简单使用方法如下:

using (IUnityContainer container = new UnityContainer())
{
    UnityConfigurationSection section = (UnityConfigurationSection)ConfigurationManager.GetSection( "unity" );
    section.Configure(container);     //...
    ILogger logger = container.Resolve( "DatabaseLogger" );
    return logger;
}

其中配置文件为

"1.0" encoding= "utf-8" ?>


    "unity" type= "Microsoft.Practices.Unity.Configuration.UnityConfigurationSection,Microsoft.Practices.Unity.Configuration" />





          "Bery.ILogger, UnityStudy" mapTo= "Bery.DatabaseLogger, UnityStudy" name= "DatabaseLogger" >

如果DatabaseLogger类中的有两个构造函数, 代码如下

public DatabaseLogger()
{
}
public DatabaseLogger(string name)
{
}

则Unity自动使用参数最多的构造函数进行创建对象, 会抛出以下异常:

Microsoft.Practices.Unity.ResolutionFailedException: Resolution of the dependency failed, type = "Bery.ILogger" , name = "DatabaseLogger" .
Exception occurred while : while resolving.
Exception is: InvalidOperationException - The type String cannot be constructed. You must configure the container to supply this value.

如果您想让它使用无参的构造函数创建, 则要使用[InjectionConstructor]特性进行修饰无参的构造函数,

[InjectionConstructor]
public DatabaseLogger()
{
}

若您想使用带参数的构造函数创建对象, 除了在构造函数上使用[InjectionConstructor]外, 还要在创建时传递参数,代码如下

using (IUnityContainer container = new UnityContainer())
{
    UnityConfigurationSection section = (UnityConfigurationSection)ConfigurationManager.GetSection( "unity" );
    section.Configure(container);
    ILogger logger = container.Resolve( "DatabaseLogger" ,
        new ParameterOverrides{
        { "name" , "logName" }
    });
    return logger;

转载于:https://www.cnblogs.com/SimonGao/p/3835284.html