Add OnPrepareResponse option w/resp header to static files doc (#2640)

* Create StartupAddHeader.cs

* Add files via upload

* Update static-files.md

* Update static-files.md

* Update StartupBrowse.cs

* Update StartupServeUnknownFileTypes.cs

* Update StartupStaticFiles.cs

* Update StartupTwoStaticFiles.cs

* Update StartupUseFileServer.cs

* Update static-files.md

aspnetcore/fundamentals/static-files.md

@@ -59,6 +59,12 @@ For a request to access *test.png*, configure the static files middleware as fol
 
 A request to `http://<app>/StaticFiles/test.png` will serve the *test.png* file.
 
+`StaticFileOptions()` can set response headers. For example, the code below sets up static file serving from the *wwwroot* folder and sets the `Cache-Control` header to make them publicly cacheable for 10 minutes (600 seconds):
+
+[!code-csharp[Main](../fundamentals/static-files/sample/StartupAddHeader.cs?name=snippet1)]
+
+![Response headers showing the Cache-Control header has been added](static-files/_static/add-header.png)
+
 ## Static file authorization
 
 The static file module provides **no** authorization checks. Any files served by it, including those under *wwwroot* are publicly available. To serve files based on authorization:

aspnetcore/fundamentals/static-files/sample/StartupAddHeader.cs

@@ -0,0 +1,32 @@
+using System.IO;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.FileProviders;
+using Microsoft.Extensions.Logging;
+
+namespace StaticFiles
+{
+    public class StartupAddHeader
+    {
+        // This method gets called by the runtime. Use this method to add services to the container.
+        public void ConfigureServices(IServiceCollection services)
+        {
+        }
+
+        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
+        #region snippet1
+        public void Configure(IApplicationBuilder app)
+        {
+            app.UseStaticFiles(new StaticFileOptions()
+            {
+                OnPrepareResponse = ctx =>
+                {
+                    ctx.Context.Response.Headers.Append("Cache-Control", "public,max-age=600");
+                }
+            });
+        }
+        #endregion
+    }
+}

aspnetcore/fundamentals/static-files/sample/StartupBrowse.cs

@@ -20,7 +20,7 @@ namespace StaticFiles
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
         #region snippet1
-        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
+        public void Configure(IApplicationBuilder app)
         {
             app.UseStaticFiles(); // For the wwwroot folder
 
@@ -40,4 +40,4 @@ namespace StaticFiles
         }
         #endregion
     }
-}
+}

aspnetcore/fundamentals/static-files/sample/StartupServeUnknownFileTypes.cs

@@ -14,9 +14,9 @@ namespace StaticFiles
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
         #region snippet1
-        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
+        public void Configure(IApplicationBuilder app)
         {
-            app.UseStaticFiles(new StaticFileOptions
+            app.UseStaticFiles(new StaticFileOptions()
             {
                 ServeUnknownFileTypes = true,
                 DefaultContentType = "image/png"
@@ -24,4 +24,4 @@ namespace StaticFiles
         }
         #endregion
     }
-}
+}

aspnetcore/fundamentals/static-files/sample/StartupStaticFiles.cs

@@ -17,10 +17,10 @@ namespace StaticFiles
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
         #region snippet1
-        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
+        public void Configure(IApplicationBuilder app)
         {
             app.UseStaticFiles();
         }
         #endregion
     }
-}
+}

aspnetcore/fundamentals/static-files/sample/StartupTwoStaticFiles.cs

@@ -17,9 +17,9 @@ namespace StaticFiles
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
         #region snippet1
-        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
+        public void Configure(IApplicationBuilder app)
         {
-            app.UseStaticFiles();
+            app.UseStaticFiles(); // For the wwwroot folder
 
             app.UseStaticFiles(new StaticFileOptions()
             {
@@ -30,4 +30,4 @@ namespace StaticFiles
         }
         #endregion
     }
-}
+}

aspnetcore/fundamentals/static-files/sample/StartupUseFileServer.cs

@@ -20,9 +20,9 @@ namespace StaticFiles
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
         #region snippet1
-        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
+        public void Configure(IApplicationBuilder app)
         {
-            app.UseStaticFiles();
+            app.UseStaticFiles(); // For the wwwroot folder
 
             app.UseFileServer(new FileServerOptions()
             {
@@ -34,4 +34,4 @@ namespace StaticFiles
         }
         #endregion
     }
-}
+}