如何将运行时参数值转换为 WebJobs 函数和 Simple Injector 中的依赖项？

Question

我有一个具有 method/trigger 的 WebJobs 函数。它的参数之一对应于 WebJobs 仪表板记录器：

public Task MyQueueHandler(TextWriter log)

如何在容器中转换或注册此 TextWriter log，以便将其注入我的另一个 class 的构造函数：

public MyLogger(TextWriter log)

有没有类似ExecutionContextScoping的方法？

Answer 1

您可以提取提供程序后面的 TextWriter，并将提供程序注入到记录器中（因为 TextWriter 显然是运行时数据，您应该直接 prevent injecting it into your components）。这允许您在调用 MyQueueHandler 时将此值设置到提供程序中。例如：

// Definition
public interface ITextWriterProvider // by lack of a better name
{
    TextWriter Current { get; }
}

// Used as dependency of MyLogger
public MyLogger(ITextWriterProvider logProvider)

// Implementation visible to your composition root
public class TextWriterProvider : ITextWriterProvider
{
    public TextWriter Current { get; set; }
}

// Registration
container.Register<ITextWriterProvider, TextWriterProvider>(Lifestyle.Scoped);
container.Register<TextWriterProvider>(Lifestyle.Scoped);

// Wrap the start of the request in a scope and assign the log value to the scope.
public Task MyQueueHandler(TextWriter log)
{
    using (AsyncScopedLifestyle.BeginScope(container))
    {
        container.GetInstance<TextWriterProvider>().Current = log;

        // execute rest of request
    }
}

作为这种设计的变体，您还可以将 TextWriterProvider 设为单例并使其值为 AsyncLocal，如下所示：

public class TextWriterProvider : ITextWriterProvider
{
    private static readonly AsyncLocal<TextWriter> current =
        new AsyncLocal<TextWriter>();

    public TextWriter Current
    { 
        get => current.Value;
        set => current.Value = value;
    }
}

// Registration
container.Register<ITextWriterProvider, TextWriterProvider>(Lifestyle.Singleton);
container.Register<TextWriterProvider>(Lifestyle.Singleton);

或者更简单：

public class TextWriterProvider : ITextWriterProvider
{
    public static readonly AsyncLocal<TextWriter> CurrentWriter =
        new AsyncLocal<TextWriter>();

    public TextWriter Current => CurrentWriter.Value;
}

// Registration
container.Register<ITextWriterProvider, TextWriterProvider>(Lifestyle.Singleton);

// Assign the log to the CurrentWriter at the start of the request
public Task MyQueueHandler(TextWriter log)
{
    TextWriterProvider.CurrentWriter = log;

    // execute rest of request
}

这些都是相同设计的变体，我们从构造函数中提取运行时数据并允许在构建对象图后对其进行解析。

如果全部失败，则可以将此运行时值直接注入对象图中。请注意，我强烈建议不要这样做，但将其视为最后的选择：

// Part of your Composition Root
public static AsyncLocal<TextWriter> Writer = new AsyncLocal<TextWriter>();

// Registration
container.Register<ILogger>(() => new MyLogger(
    Writer ?? (container.IsVerifying ? new TextWriter() : null)));

// Assign the log to the CurrentWriter at the start of the request
public Task MyQueueHandler(TextWriter log)
{
    CompositionRoot.CurrentWriter = log;

    // execute rest of request
}

如何将运行时参数值转换为 WebJobs 函数和 Simple Injector 中的依赖项？

How to convert runtime parameter value into dependency within WebJobs function and Simple Injector?

c#

dependency-injection

simple-injector

azure-webjobs