解析通過Simple Injector注冊的ASP.NET Web窗體Image Control派生類

Question

我准備將一個存儲庫實例注入一些Web.UI.WebControls.Image派生類型：

public class CustomImageControl : Image
{
    [Import]
    public ICachedNameRepository Repo { get; set; } // Null reference here

    private void DynamicImage_PreRender(object sender, EventArgs e)
    {
        ImageUrl = {some ICachedNameRepository usage}
    }
}

這也是我為測試目的而實現的默認頁面：

public partial class _Default : Page
{
    [Import]
    public ICachedNameRepository Repo { get; set; } // Totally ok here

    protected void Page_Load(object sender, EventArgs e)
    {
        {some ICachedNameRepository usage}
    }
}

我根據官方指南實施了容器引導，關於使用Control注冊而不是Page：

    private void BootStrapContainer()
    {
        var container = new Container();
        container.Options.PropertySelectionBehavior = new ImportAttributePropertySelectionBehavior();            

        container.Register<ICachedNameRepository, CachedNameRepository>();
        container.Register<CustomImageControl>(); // Also I have tried Control and Image types
        container.Register<Page>();
        var cc = container.GetInstance<CustomImageControl>(); // Correctly instantiated CachedNameRepository instance in Repo field in cc object

        container.Verify(); // OK here
        Global.Container = container;
    }

我離開了ControlInitializerModule，ImportAttributePropertySelectionBehavior和InitializeHandler例程完全從前面提到的指南中復制了

在頁面加載時，我最終得到了正確解析的默認頁面實例，其中CachedNameRepository注入了正確的位置，但我的CustomImageControl遭受了空引用。

Answer 1

這可以通過掛鈎到Page的InitComplete事件來完成。 這是我用來證明這一點的代碼。

我將CustomImageControl更改為從UserControl繼承：

public partial class CustomImageControl : UserControl
{
    [Import]
    public ICachedNameRepository Repo { get; set; }

    private void DynamicImage_PreRender(object sender, EventArgs e)
    {
    }
}

這是更新的InitializeHandler

public class Global : HttpApplication
{
    private static Container container;

    public static void InitializeHandler(IHttpHandler handler)
    {
        if (handler is Page)
        {
            Global.InitializePage((Page)handler);
        }
    }

    private static void InitializePage(Page page)
    {
        container.GetRegistration(page.GetType(), true).Registration
            .InitializeInstance(page);

        page.InitComplete += delegate { Global.InitializeControl(page); };
    }

    private static void InitializeControl(Control control)
    {
        if (control is UserControl)
        {
            container.GetRegistration(control.GetType(), true).Registration
                .InitializeInstance(control);
        }
        foreach (Control child in control.Controls)
        {
            Global.InitializeControl(child);
        }
    }

以及文檔中的其他2個更改。 一定要在引導程序中調用RegisterWebPagesAndControls

private static void RegisterWebPagesAndControls(Container container)
{
    var pageTypes =
        from assembly in BuildManager.GetReferencedAssemblies().Cast<Assembly>()
        where !assembly.IsDynamic
        where !assembly.GlobalAssemblyCache
        from type in assembly.GetExportedTypes()
        where type.IsSubclassOf(typeof(Page)) || type.IsSubclassOf(typeof(UserControl))
        where !type.IsAbstract && !type.IsGenericType
        select type;

    pageTypes.ToList().ForEach(container.Register);
}

class ImportAttributePropertySelectionBehavior : IPropertySelectionBehavior
{
    public bool SelectProperty(Type serviceType, PropertyInfo propertyInfo)
    {
        // Makes use of the System.ComponentModel.Composition assembly
        return (typeof(Page).IsAssignableFrom(serviceType) ||
            typeof(UserControl).IsAssignableFrom(serviceType)) &&
            propertyInfo.GetCustomAttributes<ImportAttribute>().Any();
    }
}