Search code examples
c#asp.net-mvcmultithreadingthread-safetyrenderpartial

Thread.Timer With HttpContext is not working


hello i'm trying to send email at a specific time i found the code. On global.asax.cs file

protected void Application_Start()
{
    ETHOS.Controllers.HomeController mail = new Controllers.HomeController();
    mail.ScheduleService();
    private void SchedularCallback(object e)
    {
        this.WriteToFile("Simple Service Log: {0}");
        getData();//Email function
        this.ScheduleService();
    }
    public void ScheduleService()
    {
        try
        {
            Schedular = new Timer(new TimerCallback(SchedularCallback));
            string mode = "DAILY";
            this.WriteToFile("Simple Service Mode: " + mode + " {0}");
            //Set the Default Time.
            //DateTime d = DateTime.Today;
            //TimeSpan t = new TimeSpan(12, 40, 00);
            //DateTime scheduledTime = d.Date + t;
            DateTime scheduledTime = DateTime.Now.AddSeconds(30);
            if (DateTime.Now > scheduledTime)
            {
                //If Scheduled Time is passed set Schedule for the next day.
                // scheduledTime = scheduledTime.AddDays(1);
                scheduledTime = scheduledTime.AddDays(1);
            }
            TimeSpan timeSpan = scheduledTime.Subtract(DateTime.Now);
            string schedule = string.Format("{0} day(s) {1} hour(s) {2} minute(s) {3} seconds(s)", timeSpan.Days, timeSpan.Hours, timeSpan.Minutes, timeSpan.Seconds);
            this.WriteToFile("Simple Service scheduled to run after: " + schedule + " {0}");
            //Get the difference in Minutes between the Scheduled and Current Time.
            int dueTime = Convert.ToInt32(timeSpan.TotalMilliseconds);

            //Change the Timer's Due Time.
            Schedular.Change(dueTime, Timeout.Infinite);
        }
        catch (Exception ex)
        {
            WriteToFile("Simple Service Error on: {0} " + ex.Message + ex.StackTrace);
        }
    }

In email function i'm sending email through gmail and on body i'm rendered partial view to string class to rendered my razor view to string

 string body = ViewRenderer.RenderPartialView("~/Views/Shared/Email.cshtml", LEM);

problem is that it doesn't getting HttpContext.Current.It show HttpContext.Current = null. I think Both are creating Thread so thats why it is not getting HttpContext so how can i use both with same httpcontext. here is the RendererView Class below

   public class ViewRenderer:ETHOS.Controllers.HomeController
      {/// <summary>
    /// Required Controller Context
    /// </summary>
    protected ControllerContext Context { get; set; }

    /// <summary>
    /// Initializes the ViewRenderer with a Context.
    /// </summary>
    /// <param name="controllerContext">
    /// If you are running within the context of an ASP.NET MVC request pass in
    /// the controller's context. 
    /// Only leave out the context if no context is otherwise available.
    /// </param>
    public ViewRenderer(ControllerContext controllerContext = null)
    {
        System.Web.HttpContext ctx =  (System.Web.HttpContext) Session["ctx"];
        // Create a known controller from HttpContext if no context is passed
        if (controllerContext == null)
        {
            if (System.Web.HttpContext.Current != null)
                controllerContext = CreateController<EmptyController>().ControllerContext;
            else
                throw new InvalidOperationException(
                    "ViewRenderer must run in the context of an ASP.NET " +
                    "Application and requires HttpContext.Current to be present.");
        }
        Context = controllerContext;
    }

    /// <summary>
    /// Renders a full MVC view to a string. Will render with the full MVC
    /// View engine including running _ViewStart and merging into _Layout        
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to render the view with</param>
    /// <returns>String of the rendered view or null on error</returns>
    public string RenderViewToString(string viewPath, object model = null)
    {
        return RenderViewToStringInternal(viewPath, model, false);
    }

    /// <summary>
    /// Renders a full MVC view to a writer. Will render with the full MVC
    /// View engine including running _ViewStart and merging into _Layout        
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to render the view with</param>
    /// <returns>String of the rendered view or null on error</returns>
    public void RenderView(string viewPath, object model, TextWriter writer)
    {
        RenderViewToWriterInternal(viewPath, writer, model, false);
    }


    /// <summary>
    /// Renders a partial MVC view to string. Use this method to render
    /// a partial view that doesn't merge with _Layout and doesn't fire
    /// _ViewStart.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to pass to the viewRenderer</param>
    /// <returns>String of the rendered view or null on error</returns>
    public string RenderPartialViewToString(string viewPath, object model = null)
    {
        return RenderViewToStringInternal(viewPath, model, true);
    }

    /// <summary>
    /// Renders a partial MVC view to given Writer. Use this method to render
    /// a partial view that doesn't merge with _Layout and doesn't fire
    /// _ViewStart.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to pass to the viewRenderer</param>
    /// <param name="writer">Writer to render the view to</param>
    public void RenderPartialView(string viewPath, object model, TextWriter writer)
    {
        RenderViewToWriterInternal(viewPath, writer, model, true);
    }

    /// <summary>
    /// Renders a partial MVC view to string. Use this method to render
    /// a partial view that doesn't merge with _Layout and doesn't fire
    /// _ViewStart.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to pass to the viewRenderer</param>
    /// <param name="controllerContext">Active Controller context</param>
    /// <returns>String of the rendered view or null on error</returns>
    public static string RenderView(string viewPath, object model = null,
                                    ControllerContext controllerContext = null)
    {
        ViewRenderer renderer = new ViewRenderer(controllerContext);
        return renderer.RenderViewToString(viewPath, model);
    }

    /// <summary>
    /// Renders a partial MVC view to the given writer. Use this method to render
    /// a partial view that doesn't merge with _Layout and doesn't fire
    /// _ViewStart.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to pass to the viewRenderer</param>
    /// <param name="writer">Writer to render the view to</param>
    /// <param name="controllerContext">Active Controller context</param>
    /// <returns>String of the rendered view or null on error</returns>
    public static void RenderView(string viewPath, TextWriter writer, object model,
                                    ControllerContext controllerContext)
    {
        ViewRenderer renderer = new ViewRenderer(controllerContext);
        renderer.RenderView(viewPath, model, writer);
    }

    /// <summary>
    /// Renders a partial MVC view to string. Use this method to render
    /// a partial view that doesn't merge with _Layout and doesn't fire
    /// _ViewStart.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to pass to the viewRenderer</param>
    /// <param name="controllerContext">Active Controller context</param>
    /// <param name="errorMessage">optional out parameter that captures an error message instead of throwing</param>
    /// <returns>String of the rendered view or null on error</returns>
    public static string RenderView(string viewPath, object model,
                                    ControllerContext controllerContext,
                                    out string errorMessage)
    {
        errorMessage = null;
        try
        {
            ViewRenderer renderer = new ViewRenderer(controllerContext);
            return renderer.RenderViewToString(viewPath, model);
        }
        catch (Exception ex)
        {
            errorMessage = ex.GetBaseException().Message;
        }
        return null;
    }

    /// <summary>
    /// Renders a partial MVC view to the given writer. Use this method to render
    /// a partial view that doesn't merge with _Layout and doesn't fire
    /// _ViewStart.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to pass to the viewRenderer</param>
    /// <param name="controllerContext">Active Controller context</param>
    /// <param name="writer">Writer to render the view to</param>
    /// <param name="errorMessage">optional out parameter that captures an error message instead of throwing</param>
    /// <returns>String of the rendered view or null on error</returns>
    public static void RenderView(string viewPath, object model, TextWriter writer,
                                    ControllerContext controllerContext,
                                    out string errorMessage)
    {
        errorMessage = null;
        try
        {
            ViewRenderer renderer = new ViewRenderer(controllerContext);
            renderer.RenderView(viewPath, model, writer);
        }
        catch (Exception ex)
        {
            errorMessage = ex.GetBaseException().Message;
        }
    }


    /// <summary>
    /// Renders a partial MVC view to string. Use this method to render
    /// a partial view that doesn't merge with _Layout and doesn't fire
    /// _ViewStart.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to pass to the viewRenderer</param>
    /// <param name="controllerContext">Active controller context</param>
    /// <returns>String of the rendered view or null on error</returns>
    public static string RenderPartialView(string viewPath, object model = null,
                                            ControllerContext controllerContext = null)
    {
        ViewRenderer renderer = new ViewRenderer(controllerContext);
        return renderer.RenderPartialViewToString(viewPath, model);
    }

    /// <summary>
    /// Renders a partial MVC view to string. Use this method to render
    /// a partial view that doesn't merge with _Layout and doesn't fire
    /// _ViewStart.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">The model to pass to the viewRenderer</param>
    /// <param name="controllerContext">Active controller context</param>
    /// <param name="writer">Text writer to render view to</param>
    /// <param name="errorMessage">optional output parameter to receive an error message on failure</param>
    public static void RenderPartialView(string viewPath, TextWriter writer, object model = null,
                                            ControllerContext controllerContext = null)
    {
        ViewRenderer renderer = new ViewRenderer(controllerContext);
        renderer.RenderPartialView(viewPath, model, writer);
    }


    /// <summary>
    /// Internal method that handles rendering of either partial or 
    /// or full views.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">Model to render the view with</param>
    /// <param name="partial">Determines whether to render a full or partial view</param>
    /// <param name="writer">Text writer to render view to</param>
    protected void RenderViewToWriterInternal(string viewPath, TextWriter writer, object model = null, bool partial = false)
    {
        // first find the ViewEngine for this view
        ViewEngineResult viewEngineResult = null;
        if (partial)
            viewEngineResult = ViewEngines.Engines.FindPartialView(Context, viewPath);
        else
            viewEngineResult = ViewEngines.Engines.FindView(Context, viewPath, null);

        if (viewEngineResult == null)
            throw new FileNotFoundException();

        // get the view and attach the model to view data
        var view = viewEngineResult.View;
        Context.Controller.ViewData.Model = model;

        var ctx = new ViewContext(Context, view,
                                    Context.Controller.ViewData,
                                    Context.Controller.TempData,
                                    writer);
        view.Render(ctx, writer);
    }

    /// <summary>
    /// Internal method that handles rendering of either partial or 
    /// or full views.
    /// </summary>
    /// <param name="viewPath">
    /// The path to the view to render. Either in same controller, shared by 
    /// name or as fully qualified ~/ path including extension
    /// </param>
    /// <param name="model">Model to render the view with</param>
    /// <param name="partial">Determines whether to render a full or partial view</param>
    /// <returns>String of the rendered view</returns>
    private string RenderViewToStringInternal(string viewPath, object model,
                                                bool partial = false)
    {
        // first find the ViewEngine for this view
        ViewEngineResult viewEngineResult = null;
        if (partial)
            viewEngineResult = ViewEngines.Engines.FindPartialView(Context, viewPath);
        else
            viewEngineResult = ViewEngines.Engines.FindView(Context, viewPath, null);

        if (viewEngineResult == null || viewEngineResult.View == null)
            throw new FileNotFoundException();//Resources.ViewCouldNotBeFound);

        // get the view and attach the model to view data
        var view = viewEngineResult.View;
        Context.Controller.ViewData.Model = model;

        string result = null;

        using (var sw = new StringWriter())
        {
            var ctx = new ViewContext(Context, view,
                                        Context.Controller.ViewData,
                                        Context.Controller.TempData,
                                        sw);
            view.Render(ctx, sw);
            result = sw.ToString();
        }

        return result;
    }


    /// <summary>
    /// Creates an instance of an MVC controller from scratch 
    /// when no existing ControllerContext is present       
    /// </summary>
    /// <typeparam name="T">Type of the controller to create</typeparam>
    /// <returns>Controller for T</returns>
    /// <exception cref="InvalidOperationException">thrown if HttpContext not available</exception>
    public static T CreateController<T>(RouteData routeData = null, params object[] parameters)
                where T : Controller, new()
    {
        // create a disconnected controller instance
        T controller = (T)Activator.CreateInstance(typeof(T), parameters);

        // get context wrapper from HttpContext if available
        HttpContextBase wrapper = null;
        if (System.Web.HttpContext.Current != null)
            wrapper = new HttpContextWrapper(System.Web.HttpContext.Current);
        else
            throw new InvalidOperationException(
                "Can't create Controller Context if no active HttpContext instance is available.");

        if (routeData == null)
            routeData = new RouteData();

        // add the controller routing if not existing
        if (!routeData.Values.ContainsKey("controller") && !routeData.Values.ContainsKey("Controller"))
            routeData.Values.Add("controller", controller.GetType().Name
                                                        .ToLower()
                                                        .Replace("controller", ""));

        controller.ControllerContext = new ControllerContext(wrapper, routeData, controller);
        return controller;
    }

}

/// <summary>
/// Empty MVC Controller instance used to 
/// instantiate and provide a new ControllerContext
/// for the ViewRenderer
/// </summary>
public class EmptyController : Controller
{
}

Solution

  • The HttpContext is only available within the lifetime of an HTTP request. It is not possible to use it outside in such background threads. Also it is considered bad practice to implement recurring background tasks in an ASP.NET applications. The recommended approach is to off-load this task from your web application and put it in a Windows Service or a Console Application that will be executed at regular intervals by the Windows Scheduler.

    That being said, if you decide to go against the recommended approaches and still insist on doing this, you might consider using the Razor engine outside of an ASP.NET application so that you don't depend on an HttpContext.