Razor Pages Filters

aspnetcore/mvc/razor-pages/filter.md

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+---
+title: Filter methods for Razor Pages in ASP.NET Core
+author: Rick-Anderson
+description: Learn how to create filter methods for Razor Pages in ASP.NET Core.
+manager: wpickett
+ms.author: riande
+ms.date: 4/5/2018
+ms.prod: asp.net-core
+ms.technology: aspnet
+ms.topic: content
+uid: mvc/razor-pages/filter
+---
+# Filter methods for Razor Pages in ASP.NET Core
+
+By [Rick Anderson](https://twitter.com/RickAndMSFT)
+
+Razor Page filters [IPageFilter](/dotnet/api/microsoft.aspnetcore.mvc.filters.ipagefilter?view=aspnetcore-2.0) and [IAsyncPageFilter](/dotnet/api/microsoft.aspnetcore.mvc.filters.iasyncpagefilter?view=aspnetcore-2.0) allow Razor Pages to run code before and after a Razor Page handler is run. Razor Page filters are similar to [ASP.NET Core MVC action filters](xref:mvc/controllers/filters#action-filters).
+
+Razor Page filters:
+
+* Run code after a handler method has been selected, but before model binding occurs.
+* Run code before the handler method executes, after model binding is complete.
+* Run code after the handler method executes.
+* Can be implemented on a page or globally.
+
+Code can be run before a handler method executes using the page constructor or middleware, but only Razor Page filters have access to [HttpContext](/dotnet/api/microsoft.aspnetcore.mvc.razorpages.pagemodel.httpcontext?view=aspnetcore-2.0#Microsoft_AspNetCore_Mvc_RazorPages_PageModel_HttpContext). Filters have a [FilterContext](/dotnet/api/microsoft.aspnetcore.mvc.filters.filtercontext?view=aspnetcore-2.0) derived parameter, which provides access to `HttpContext`.
+
+[View or download sample code](https://github.com/aspnet/Docs/tree/live/aspnetcore/tutorials/razor-pages/razor-pages-start/sample/RazorPagesMovie) ([how to download](xref:tutorials/index#how-to-download-a-sample))
+
+Razor Page filters provide the following methods, which can be applied globally or at the page level:
+
+* Synchronous methods:
+
+    * [OnPageHandlerSelected](/dotnet/api/microsoft.aspnetcore.mvc.filters.ipagefilter.onpagehandlerselected?view=aspnetcore-2.0) : Called after a handler method has been selected, but before model binding occurs.
+    * [OnPageHandlerExecuting](/dotnet/api/microsoft.aspnetcore.mvc.filters.ipagefilter.onpagehandlerexecuting?view=aspnetcore-2.0) : Called before the handler method executes, after model binding is complete.
+    * [OnPageHandlerExecuted](/dotnet/api/microsoft.aspnetcore.mvc.filters.ipagefilter.onpagehandlerexecuted?view=aspnetcore-2.0) : Called after the handler method executes, before the action result.
+
+* Asynchronous methods:
+
+    * [OnPageHandlerSelectionAsync](/dotnet/api/microsoft.aspnetcore.mvc.filters.iasyncpagefilter.onpagehandlerselectionasync?view=aspnetcore-2.0) : Called asynchronously after the handler method has been selected, but before model binding occurs.
+    * [OnPageHandlerExecutionAsync](/dotnet/api/microsoft.aspnetcore.mvc.filters.iasyncpagefilter.onpagehandlerexecutionasync?view=aspnetcore-2.0) : Called asynchronously before the handler method is invoked, after model binding is complete.
+
+> [!NOTE]
+> Implement **either** the synchronous or the async version of a filter interface, not both. The framework checks first to see if the filter implements the async interface, and if so, it calls that. If not, it calls the synchronous interface's method(s). If both interfaces are implemented, only the async methods are be called. The same rule applies to overrides in pages, implement the synchronous or the async version of the override, not both.
+
+## Implement Razor Page filters globally
+
+The following code implements an `IAsyncPageFilter`:
+
+[!code-csharp[Main](filter/sample/PageFilter/Filters/SampleAsyncPageFilter.cs?name=snippet1)]
+
+In the preceding code, [ILogger](/dotnet/api/microsoft.extensions.logging.ilogger?view=aspnetcore-2.0) is not required. It's used in the sample to provide trace information for the application.
+
+The following code enables the `SampleAsyncPageFilter` in the `Startup` class:
+
+[!code-csharp[Main](filter/sample/PageFilter/Startup.cs?name=snippet2&highlight=11)]
+
+The following code shows the complete `Startup` class:
+
+[!code-csharp[Main](filter/sample/PageFilter/Startup.cs?name=snippet1)]
+
+The following code implements the synchronous `IPageFilter`:
+
+[!code-csharp[Main](filter/sample/PageFilter/Filters/SamplePageFilter.cs?name=snippet1)]
+
+The following code enables the `SamplePageFilter`:
+
+[!code-csharp[Main](filter/sample/PageFilter/StartupSync.cs?name=snippet2&highlight=11)]
+
+## Implement Razor Page filters by overriding page handlers
+
+The following code overrides the synchronous Razor Page filters:
+
+[!code-csharp[Main](filter/sample/PageFilter/Pages/Index.cshtml.cs)]
+
+The following code overrides the asynchronous Razor Page filters:
+
+[!code-csharp[Main](filter/sample/PageFilter/Pages/Contact.cshtml.cs)]

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Filters/GlobalFiltersLogger.cs

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+// This class is used to create the logger type in Startup.
+namespace PageFilter.Filters
+{
+    public class GlobalFiltersLogger
+    {
+    }
+}

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Filters/SampleAsyncPageFilter.cs

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+#region snippet1
+using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.Extensions.Logging;
+using System.Threading.Tasks;
+
+namespace PageFilter.Filters
+{
+    public class SampleAsyncPageFilter : IAsyncPageFilter
+    {
+        private readonly ILogger _logger;
+
+        public SampleAsyncPageFilter(ILogger logger)
+        {
+            _logger = logger;
+        }
+
+        public async Task OnPageHandlerSelectionAsync(
+                                            PageHandlerSelectedContext context)
+        {
+            _logger.LogDebug("Global OnPageHandlerSelectionAsync called.");
+            await Task.CompletedTask;
+        }
+
+        public async Task OnPageHandlerExecutionAsync(
+                                            PageHandlerExecutingContext context,
+                                            PageHandlerExecutionDelegate next)
+        {
+            _logger.LogDebug("Global OnPageHandlerExecutionAsync called.");
+            await next.Invoke();
+        }
+    }
+}
+#endregion

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Filters/SamplePageFilter.cs

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+#region snippet1
+using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.Extensions.Logging;
+
+namespace PageFilter.Filters
+{
+    public class SamplePageFilter : IPageFilter
+    {
+        private readonly ILogger _logger;
+
+        public SamplePageFilter(ILogger logger)
+        {
+            _logger = logger;
+        }
+
+        public void OnPageHandlerSelected(PageHandlerSelectedContext context)
+        {
+            _logger.LogDebug("Global sync OnPageHandlerSelected called.");
+        }
+
+        public void OnPageHandlerExecuting(PageHandlerExecutingContext context)
+        {
+            _logger.LogDebug("Global sync PageHandlerExecutingContext called.");
+        }
+
+        public void OnPageHandlerExecuted(PageHandlerExecutedContext context)
+        {
+            _logger.LogDebug("Global sync OnPageHandlerExecuted called.");
+        }
+    }
+}
+#endregion

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/PageFilter.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+  </PropertyGroup>
+
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.App" Version="2.1.0-preview2-30457" />
+  </ItemGroup>
+
+
+</Project>

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/About.cshtml

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+@page
+@model AboutModel
+@{
+    ViewData["Title"] = "About";
+}
+<h2>@ViewData["Title"]</h2>
+<h3>@Model.Message</h3>
+
+<p>Use this area to provide additional information.</p>
+
+<div class="col-md-12">
+    <form method="post">
+        <input type="submit" id="send" value="Post" />
+    </form>
+    <p></p>
+    <ul id="messages" style="list-style-type:none;"></ul>
+</div>

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/About.cshtml.cs

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+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.Extensions.Logging;
+
+namespace PageFilter.Pages
+{
+    public class AboutModel : PageModel
+    {
+        private readonly ILogger _logger;
+
+        public AboutModel(ILogger<AboutModel> logger)
+        {
+            _logger = logger;
+        }
+
+        public string Message { get; set; }
+
+        public void OnGet()
+        {
+            Message = "Your application description page.";
+            _logger.LogDebug("About/OnGet");
+        }
+
+        public void OnPost()
+        {
+            _logger.LogDebug("About/OnPost");
+        }
+    }
+}

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/Contact.cshtml

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+@page
+@model ContactModel
+@{
+    ViewData["Title"] = "Contact";
+}
+<h2>@ViewData["Title"]</h2>
+<h3>@Model.Message</h3>
+
+<address>
+    One Microsoft Way<br />
+    Redmond, WA 98052-6399<br />
+    <abbr title="Phone">P:</abbr>
+    425.555.0100
+</address>
+
+<address>
+    <strong>Support:</strong> <a href="mailto:Support@example.com">Support@example.com</a><br />
+    <strong>Marketing:</strong> <a href="mailto:Marketing@example.com">Marketing@example.com</a>
+</address>

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/Contact.cshtml.cs

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+using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.Extensions.Logging;
+using System.Threading.Tasks;
+
+namespace PageFilter.Pages
+{
+    public class ContactModel : PageModel
+    {
+        private readonly ILogger _logger;
+
+        public ContactModel(ILogger<ContactModel> logger)
+        {
+            _logger = logger;
+        }
+        public string Message { get; set; }
+
+        public async Task OnGetAsync()
+        {
+            Message = "Your contact page.";
+            _logger.LogDebug("Contact/OnGet");
+            await Task.CompletedTask;
+        }
+
+        public override async Task OnPageHandlerSelectionAsync(
+            PageHandlerSelectedContext context)
+        {
+            _logger.LogDebug("ContactModel/OnPageHandlerSelectionAsync called.");
+            await Task.CompletedTask;
+        }
+
+        public override async Task OnPageHandlerExecutionAsync(
+            PageHandlerExecutingContext context,
+           PageHandlerExecutionDelegate next)
+        {
+            _logger.LogDebug("ContactModel/OnPageHandlerExecutionAsync called.");
+            await next.Invoke();
+        }
+    }
+}

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/Error.cshtml

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+@page
+@model ErrorModel
+@{
+    ViewData["Title"] = "Error";
+}
+
+<h1 class="text-danger">Error.</h1>
+<h2 class="text-danger">An error occurred while processing your request.</h2>
+
+@if (Model.ShowRequestId)
+{
+    <p>
+        <strong>Request ID:</strong> <code>@Model.RequestId</code>
+    </p>
+}
+
+<h3>Development Mode</h3>
+<p>
+    Swapping to <strong>Development</strong> environment will display more detailed information about the error that occurred.
+</p>
+<p>
+    <strong>Development environment should not be enabled in deployed applications</strong>, as it can result in sensitive information from exceptions being displayed to end users. For local debugging, development environment can be enabled by setting the <strong>ASPNETCORE_ENVIRONMENT</strong> environment variable to <strong>Development</strong>, and restarting the application.
+</p>

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/Error.cshtml.cs

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+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+
+namespace PageFilter.Pages
+{
+    public class ErrorModel : PageModel
+    {
+        public string RequestId { get; set; }
+
+        public bool ShowRequestId => !string.IsNullOrEmpty(RequestId);
+
+        [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
+        public void OnGet()
+        {
+            RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier;
+        }
+    }
+}

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/Index.cshtml

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+@page "{id:int?}"
+@model IndexModel
+@{
+    ViewData["Title"] = "Home page";
+}
+
+<h2>@ViewData["Title"]</h2>
+<h3>@Model.Message</h3>
+
+<p>Simplified Index page.</p>

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/Index.cshtml.cs

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+using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.Extensions.Logging;
+
+namespace PageFilter.Pages
+{
+    public class IndexModel : PageModel
+    {
+        private readonly ILogger _logger;
+
+        public IndexModel(ILogger<IndexModel> logger)
+        {
+            _logger = logger;
+        }
+        public string Message { get; set; }
+
+        public void OnGet()
+        {
+            _logger.LogDebug("IndexModel/OnGet");
+        }
+
+        public override void OnPageHandlerSelected(PageHandlerSelectedContext context)
+        {
+            _logger.LogDebug("IndexModel/OnPageHandlerSelected");          
+        }
+
+        public override void OnPageHandlerExecuting(PageHandlerExecutingContext context)
+        {
+            Message = "Message set in handler executing";
+            _logger.LogDebug("IndexModel/OnPageHandlerExecuting");
+        }
+
+
+        public override void OnPageHandlerExecuted(PageHandlerExecutedContext context)
+        {
+            _logger.LogDebug("IndexModel/OnPageHandlerExecuted");
+        }
+    }
+}

aspnetcore/mvc/razor-pages/filter/sample/PageFilter/Pages/Privacy.cshtml

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+@page
+@model PrivacyModel
+@{
+    ViewData["Title"] = "Privacy Policy";
+}
+<h2>@ViewData["Title"]</h2>
+
+<p>Use this page to detail your site's privacy policy.</p>