C# Func<> Delegate property setter 问题

Question

我正在尝试使用如下委托(delegate)返回类型为 IDocumentTemplateProvider 的对象:

public static class DocumentTemplateProvider
{
    private static Func<IDocumentTemplateProvider> _docTemplateProvider;

    public static void SetdocTemplateProvider(Func<IDocumentTemplateProvider> docTemplateProvider)
    {
        _docTemplateProvider = docTemplateProvider;
    }

    public static void SetDocTemplateProvider<T>() where T : IDocumentTemplateProvider, new()
    {
        _docTemplateProvider = () => new T();
    }

    public static IDocumentTemplateProvider TemplateProvider
    {
        get { return _docTemplateProvider(); }
    }
}

但是当我调用它时:

private static readonly IDocumentTemplateProvider _template = DocumentTemplateProvider.TemplateProvider;

_template 始终为空。我是 C# Func<> 代表的新手，所以我看不出我做错了什么。有人能指出我正确的方向吗？

谢谢

更新:为了清除 ant 混淆，我添加了完整代码，其中 _template 被初始化并按原样使用:

 public class DocumentModule : IHttpModule
{
        private static readonly IDocumentTemplateProvider _template = DocumentTemplateProvider.TemplateProvider;

        public void Init(HttpApplication context)
        {
            context.BeginRequest += OnBeginRequest;
            context.EndRequest += OnEndRequest;
        }      

        public void Init(HttpApplication context)
        {
            context.BeginRequest += OnBeginRequest;
            context.EndRequest += OnEndRequest;
        }

        private void OnBeginRequest(object sender, EventArgs eventArgs)
        {
            _template.SetProvider();
        }

        private void OnEndRequest(object sender, EventArgs e)
        {
            _template.Finalize();
        }        

        public void Dispose()
        {
        }
}

Answer 1

它是空的，因为它从未被设置过。您有两个设置 _docTemplateProvider 变量的 Void 方法，因此您需要先调用它们，如下面的示例代码

class Program
{
    private static void Main()
    {
        DocumentTemplateProvider.SetDocTemplateProvider<Test>();
        //OR
        DocumentTemplateProvider.SetdocTemplateProvider(() => new Test());

        IDocumentTemplateProvider _template = DocumentTemplateProvider.TemplateProvider;

        Console.ReadLine();
    }

    public static class DocumentTemplateProvider
    {
        private static Func<IDocumentTemplateProvider> _docTemplateProvider;

        public static void SetdocTemplateProvider(Func<IDocumentTemplateProvider> docTemplateProvider)
        {
            _docTemplateProvider = docTemplateProvider;
        }

        public static void SetDocTemplateProvider<T>() where T : IDocumentTemplateProvider, new()
        {
            _docTemplateProvider = () => new T();
        }

        public static IDocumentTemplateProvider TemplateProvider
        {
            get { return _docTemplateProvider(); }
        }
    }
}

internal interface IDocumentTemplateProvider
{
}

public class Test : IDocumentTemplateProvider
{
}