使用Unity将对象注入IValueConverter实例

Question

我在Silverlight 5项目中有一个IValueConverter实例,它将自定义数据转换为不同的颜色.我需要从数据库中读取实际的颜色值(因为这些可以由用户编辑).

由于Silverlight使用异步调用通过Entity Framework从数据库加载数据,因此我创建了一个简单的存储库,它保存数据库中的值.

界面:

public interface IConfigurationsRepository
{
    string this[string key] { get; }
}

实施:

public class ConfigurationRepository : IConfigurationsRepository
{
    private readonly TdTerminalService _service = new TdTerminalService();

    public ConfigurationRepository()
    {
        ConfigurationParameters = new Dictionary<string, string>();
        _service.LoadConfigurations().Completed += (s, e) =>
            {
                var loadOperation = (LoadOperation<Configuration>) s;
                foreach (Configuration configuration in loadOperation.Entities)
                {
                    ConfigurationParameters[configuration.ParameterKey] = configuration.ParameterValue;
                }
            };
    }

    private IDictionary<string, string> ConfigurationParameters { get; set; }

    public string this[string key]
    {
        get
        {
            return ConfigurationParameters[key];
        }
    }
}

现在我想使用Unity将我的存储库实例注入IValueConverter实例...

App.xaml.cs:

private void RegisterTypes()
{
    _container = new UnityContainer();
    IConfigurationsRepository configurationsRepository = new ConfigurationRepository();
    _container.RegisterInstance<IConfigurationsRepository>(configurationsRepository);
}

的IValueConverter:

public class SomeValueToBrushConverter : IValueConverter
{
    [Dependency]
    private ConfigurationRepository ConfigurationRepository { get; set; }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
       switch ((SomeValue)value)
        {
            case SomeValue.Occupied:
                return new SolidColorBrush(ConfigurationRepository[OccupiedColor]);
            default:
                throw new ArgumentException();
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

问题是,我没有在转换器实例中获得相同的Unity-Container(即存储库未注册).

Answer 1

可以使用a MarkupExtension来解析DI容器中的依赖关系:

public class IocResolver : MarkupExtension
{
    public IocResolver()
    { }

    public IocResolver(string namedInstance)
    {
        NamedInstance = namedInstance;
    }

    [ConstructorArgument("namedInstance")]
    public string NamedInstance { get; set; }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        var provideValueTarget = (IProvideValueTarget)serviceProvider
            .GetService(typeof(IProvideValueTarget));

        // Find the type of the property we are resolving
        var targetProperty = provideValueTarget.TargetProperty as PropertyInfo;

        if (targetProperty == null)
            throw new InvalidProgramException();

        Debug.Assert(Resolve != null, "Resolve must not be null. Please initialize resolving method during application startup.");
        Debug.Assert(ResolveNamed != null, "Resolve must not be null. Please initialize resolving method during application startup.");

        // Find the implementation of the type in the container
        return NamedInstance == null
            ? (Resolve != null ? Resolve(targetProperty.PropertyType) : DependencyProperty.UnsetValue)
            : (ResolveNamed != null ? ResolveNamed(targetProperty.PropertyType, NamedInstance) : DependencyProperty.UnsetValue);
    }

    public static Func<Type, object> Resolve { get; set; }
    public static Func<Type, string, object> ResolveNamed { get; set; }
}

必须在应用程序启动期间初始化IocResolver,如:

IocResolver.Resolve = kernel.Get; 
IocResolver.ResolveNamed = kernel.GetNamed;
// or what ever your DI container looks like

之后,您可以在XAML中使用它在XAML中注入依赖:

<!-- Resolve an instance based on the type of property 'SomeValueToBrushConverter' -->
<MyConverter SomeValueToBrushConverter="{services:IocResolver}" />

<!-- Resolve a named instance based on the type of property 'SomeValueToBrushConverter' and the name 'MyName' -->
<MyConverter SomeValueToBrushConverter="{services:IocResolver  NamedInstance=MyName}" />

Answer 2

根据您的评论，您需要使用 ServiceLocator 来获取 ConfigurationRepository 的实例，因为 Converter 的实例不是由 Unity 创建的 xc2xb4t，而是由 Silverlight/XAML 引擎创建。

\n\n

因此，用 DependencyAttribute 修饰的属性将不会被注入\xc2\xb4t。

\n\n

C＃

\n\n

public class SomeValueToBrushConverter : IValueConverter\n{\n    public SomeValueToBrushConverter(){\n      ConfigurationRepository = ServiceLocator.Current.GetInstance<ConfigurationRepository>();\n    }\n\n    private ConfigurationRepository ConfigurationRepository { get; set; }\n}\n

\n\n

在您的 RegisterTypes 方法中，您需要配置 ServiceLocator：

\n\n

_container = new UnityContainer();\nUnityServiceLocator locator = new UnityServiceLocator(_container);\nServiceLocator.SetLocatorProvider(() => locator);\n

\n