New Feature in asp.net 4: Using Browser Capabilities Providers
In ASP.NET version 3.5 Service Pack 1, you can define the capabilities that a browser has in the following ways:
· At the machine level, you create or update a .browser XML file in the following folder:
\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG\Browsers
After you define the browser capability, you run the following command from the Visual Studio Command Prompt in order to rebuild the browser capabilities assembly and add it to the GAC:
aspnet_regbrowsers.exe –I c
· For an individual application, you create a .browser file in the application’s App_Browsers folder.
These approaches require you to change XML files, and for machine-level changes, you must restart the application after you run the aspnet_regbrowsers.exe process.
ASP.NET 4 includes a feature referred to as browser capabilities providers. As the name suggests, this lets you build a provider that in turn lets you use your own code to determine browser capabilities.
In practice, developers often do not define custom browser capabilities. Browser files are hard to update, the process for updating them is fairly complicated, and the XML syntax for .browser files can be complex to use and define. What would make this process much easier is if there were a common browser definition syntax, or a database that contained up-to-date browser definitions, or even a Web service for such a database. The new browser capabilities providers feature makes these scenarios possible and practical for third-party developers.
There are two main approaches for using the new ASP.NET 4 browser capabilities provider feature: extending the ASP.NET browser capabilities definition functionality, or totally replacing it. The following sections describe first how to replace the functionality, and then how to extend it.
Posted in: asp.net | Tags: asp.net 4.0 config new feature broser capabilities providers provider gac aspnet_regbrowsersReplacing the ASP.NET Browser Capabilities Functionality in asp.net 4.0
To replace the ASP.NET browser capabilities definition functionality completely, follow these steps:
1. Create a provider class that derives from HttpCapabilitiesProvider and that overrides the GetBrowserCapabilities method, as in the following example:
public class CustomProvider : HttpCapabilitiesProvider
{
public override HttpBrowserCapabilities
GetBrowserCapabilities(HttpRequest request)
{
HttpBrowserCapabilities browserCaps = new HttpBrowserCapabilities();
Hashtable values = new Hashtable(180, StringComparer.OrdinalIgnoreCase);
values[String.Empty] = request.UserAgent;
values["browser"] = "MyCustomBrowser";
browserCaps.Capabilities = values;
return browserCaps;
}
}
The code in this example creates a new HttpBrowserCapabilities object, specifying only the capability named browser and setting that capability to MyCustomBrowser.
2. Register the provider with the application.
In order to use a provider with an application, you must add the provider attribute to the browserCaps section in the Web.config or Machine.config files. (You can also define the provider attributes in a location element for specific directories in application, such as in a folder for a specific mobile device.) The following example shows how to set the provider attribute in a configuration file:
<system.web>
<browserCaps provider="ClassLibrary2.CustomProvider, ClassLibrary2,
Version=1.0.0.0, Culture=neutral" />
</system.web>
Another way to register the new browser capability definition is to use code, as shown in the following example:
void Application_Start(object sender, EventArgs e)
{
HttpCapabilitiesBase.BrowserCapabilitiesProvider =
new ClassLibrary2.CustomProvider();
// ...
}
This code must run in the Application_Start event of the Global.asax file. Any change to the BrowserCapabilitiesProvider class must occur before any code in the application executes, in order to make sure that the cache remains in a valid state for the resolved HttpCapabilitiesBase object.
Caching the HttpBrowserCapabilities Object
The preceding example has one problem, which is that the code would run each time the custom provider is invoked in order to get the HttpBrowserCapabilities object. This can happen multiple times during each request. In the example, the code for the provider does not do much. However, if the code in your custom provider performs significant work in order to get the HttpBrowserCapabilities object, this can result in huge overhead. To prevent this from happening, you can cache the HttpBrowserCapabilities object. Follow these steps:
1. Create a class that derives from HttpCapabilitiesProvider, like the one in the following example:
public class CustomProvider : HttpCapabilitiesProvider
{
public override HttpBrowserCapabilities
GetBrowserCapabilities(HttpRequest request)
{
string cacheKey = BuildCacheKey();
int cacheTime = GetCacheTime();
HttpBrowserCapabilities browserCaps =
HttpContext.Current.Cache[cacheKey] as
HttpBrowserCapabilities;
if (browserCaps == null)
{
HttpBrowserCapabilities browserCaps = new
HttpBrowserCapabilities();
Hashtable values = new Hashtable(180,
StringComparer.OrdinalIgnoreCase);
values[String.Empty] = request.UserAgent;
values["browser"] = "MyCustomBrowser";
browserCaps.Capabilities = values;
HttpContext.Current.Cache.Insert(cacheKey,
browserCaps, null, DateTime.MaxValue,
TimeSpan.FromSeconds(cacheTime));
}
return browserCaps;
}
}
In the example, the code generates a cache key by calling a custom BuildCacheKey method, and it gets the length of time to cache by calling a custom GetCacheTime method. The code then adds the resolved HttpBrowserCapabilities object to the cache. The object can be retrieved from the cache and reused on subsequent requests that need your custom provider.
2. Register the provider with the application as described in the preceding procedure.
Posted in: asp.net | Tags: asp.net asp.net 4.0 replace broser capabilities functionality httpcapabilitiesprovider httpbrowsercapabilitiesExtending ASP.NET Browser Capabilities Functionality in asp.net 4.0
The previous section described how to create a new HttpBrowserCapabilities object in ASP.NET 4. You can also extend the ASP.NET browser capabilities functionality by adding new browser capabilities definitions to those that are already in ASP.NET. You can do this without using the XML browser definitions. The following procedure shows how.
1. Create a class that derives from HttpCapabilitiesEvaluator and that overrides the GetBrowserCapabilities method, like the one in the following example:
public class CustomProvider : HttpCapabilitiesEvaluator
{
public override HttpBrowserCapabilities
GetBrowserCapabilities(HttpRequest request)
{
HttpBrowserCapabilities browserCaps =
base.GetHttpBrowserCapabilities(request);
if (browserCaps.Browser == "Unknown")
{
browserCaps = MyBrowserCapabilitiesEvaulator(request);
}
return browserCaps;
}
}
This code first uses the ASP.NET browser capabilities functionality to try to identify the browser. However, if no browser is identified based on the information defined in the request (that is, if the Browser property of the HttpBrowserCapabilities object is the string “Unknown”), the code calls the custom provider (MyBrowserCapabilitiesEvaluator) to identify the browser.
2. Register the provider with the application as described in the previous example.
Extending Browser Capabilities Functionality by Adding New Capabilities to Existing Capabilities Definitions
In addition to creating a custom browser definition provider and to dynamically creating new browser definitions, you can extend existing browser definitions with additional capabilities. This lets you use a definition that is close to what you want but lacks only a few capabilities. To do this, use the following steps.
1. Create a class that derives from HttpCapabilitiesEvaluator and that overrides the GetBrowserCapabilities method, like the one in the following example:
public class CustomProvider : HttpCapabilitiesEvaluator
{
public override HttpBrowserCapabilities
GetBrowserCapabilities(HttpRequest request)
{
HttpBrowserCapabilities browserCaps =
base.GetHttpBrowserCapabilities(request);
browserCaps.Frames = true;
browserCaps.Capabilities["MultiTouch"] = "true";
return browserCaps;
}
}
The example code extends the existing ASP.NET HttpCapabilitiesEvaluator class and gets the HttpBrowserCapabilities object that matched the current request definition by using the following code:
HttpBrowserCapabilities browserCaps =
base.GetHttpBrowserCapabilities(request);
The code can then add or modify a capability for this browser. There are two ways to specify a new browser capability:
· Add a key/value pair to the IDictionary object that is exposed by the Capabilities property of the HttpCapabilitiesBase object. In the previous example, the code adds a capability named MultiTouch with a value of true.
· Set existing properties of the HttpCapabilitiesBase object. In the previous example, the code sets the Frames property to true. This property is simply an accessor for the IDictionary object that is exposed by the Capabilities property.
Note This model applies to any property of HttpBrowserCapabilities, including control adapters.
2. Register the provider with the application as described in the earlier procedure.
Posted in: asp.net | Tags: asp.net 4.0 broser capabilities httpbrowsercapabilities httpcapabilitiesevaluator getbrowsercapabilities extend key valueRouting in ASP.NET 4
ASP.NET 4 adds built-in support for using routing with Web Forms. Routing lets you configure an application to accept request URLs that do not map to physical files. Instead, you can use routing to define URLs that are meaningful to users and that can help with search-engine optimization (SEO) for your application. For example, the URL for a page that displays product categories in an existing application might look like the following example:
http://website/products.aspx?categoryid=12
By using routing, you can configure the application to accept the following URL to render the same information:
http://website/products/software
Routing has been available starting with ASP.NET 3.5 SP1. However, ASP.NET 4 includes some features that make it easier to use routing, including the following:
· The PageRouteHandler class, which is a simple HTTP handler that you use when you define routes. The class passes data to the page that the request is routed to.
· The new properties HttpRequest.RequestContext and Page.RouteData (which is a proxy for the HttpRequest.RequestContext.RouteData object). These properties make it easier to access information that is passed from the route.
· The following new expression builders, which are defined in System.Web.Compilation.RouteUrlExpressionBuilder and System.Web.Compilation.RouteValueExpressionBuilder:
· RouteUrl, which provides a simple way to create a URL that corresponds to a route URL format within an ASP.NET server control.
· RouteValue, which provides a simple way to extract information from the RouteContext object.
· The RouteParameter class, which makes it easier to pass data contained in a RouteContext object to a query for a data source control (similar to FormParameter).
Routing for Web Forms Pages
The following example shows how to define a Web Forms route by using the new MapPageRoute method of the Route class:
public class Global : System.Web.HttpApplication
{
void Application_Start(object sender, EventArgs e)
{
RouteTable.Routes.MapPageRoute("SearchRoute",
"search/{searchterm}", "~/search.aspx");
RouteTable.Routes.MapPageRoute("UserRoute",
"users/{username}", "~/users.aspx");
}
}
ASP.NET 4 Beta 2 introduces the MapPageRoute method. The following example is equivalent to the SearchRoute definition shown in the previous example, but uses the PageRouteHandler class.
RouteTable.Routes.Add("SearchRoute", new Route("search/{searchterm}",
new PageRouteHandler("~/search.aspx")));
The code in the example maps the route to a physical page (in the first route, to ~/search.aspx). The first route definition also specifies that the parameter named searchterm should be extracted from the URL and passed to the page.
The MapPageRoute method supports the following method overloads:
· MapPageRoute(string routeName, string routeUrl, string physicalFile, bool checkPhysicalUrlAccess)
· MapPageRoute(string routeName, string routeUrl, string physicalFile, bool checkPhysicalUrlAccess, RouteValueDictionary defaults)
· MapPageRoute(string routeName, string routeUrl, string physicalFile, bool checkPhysicalUrlAccess, RouteValueDictionary defaults, RouteValueDictionary constraints)
The checkPhysicalUrlAccess parameter specifies whether the route should check the security permissions for the physical page being routed to (in this case, search.aspx) and the permissions on the incoming URL (in this case, search/{searchterm}). If the value of checkPhysicalUrlAccess is false, only the permissions of the incoming URL will be checked. These permissions are defined in the Web.config file with settings such as the following:
<configuration>
<location path="search.aspx">
<system.web>
<authorization>
<allow roles="admin"/>
<deny users="*"/>
</authorization>
</system.web>
</location>
<location path="search">
<system.web>
<authorization>
<allow users="*"/>
</authorization>
</system.web>
</location>
</configuration>
In the example configuration, access is denied to the physical page search.aspx for all users except those who are in the admin role. When the checkPhysicalUrlAccess parameter is set to true (which is its default value), only admin users are allowed to access the URL /search/{searchterm}, because the physical page search.aspx is restricted to users in that role. If checkPhysicalUrlAccess is set to false and the site is configured as shown in the previous example, all authenticated users are allowed to access the URL /search/{searchterm}.
Posted in: asp.net | Tags: xml asp.net asp.net 4.0 eventargs routing pageroutehandler httprequest requestcontext routevalueexpressionbuilder web form page authorization location configurationReading Routing Information in a Web Forms Page
In the code of the Web Forms physical page, you can access the information that routing has extracted from the URL (or other information that another object has added to the RouteData object) by using two new properties: HttpRequest.RequestContext and Page.RouteData. (Page.RouteData wraps HttpRequest.RequestContext.RouteData.) The following example shows how to use Page.RouteData.
protected void Page_Load(object sender, EventArgs e)
{
string searchterm = Page.RouteData.Values["searchterm"] as string;
label1.Text = searchterm;
}
The code extracts the value that was passed for the searchterm parameter, as defined in the example route earlier. Consider the following request URL:
http://localhost/search/scott/
When this request is made, the word "scott" would be rendered in the search.aspx page.
Accessing Routing Information in Markup
The method described in the previous section shows how to get route data in code in a Web Forms page. You can also use expressions in markup that give you access to the same information. Expression builders have been described as a "hidden gem of ASP.NET" (see the entry Express Yourself With Custom Expression Builders on Phil Haack's blog). It is unfortunate that they are not better known, because expression builders are a powerful and elegant way to work with declarative code.
ASP.NET 4 includes two new expression builders for Web Forms routing. The following example shows how to use them.
<asp:HyperLink ID="HyperLink1" runat="server"
NavigateUrl="<%$RouteUrl:SearchTerm=scott%>">Search for Scott</asp:HyperLink>
In the example, the RouteUrl expression is used to define a URL that is based on a route parameter. This saves you from having to hard-code the complete URL into the markup, and lets you change the URL structure later without requiring any change to this link.
Based on the route defined earlier, this markup generates the following URL:
http://localhost/search/scott
ASP.NET automatically works out the correct route (that is, it generates the correct URL) based on the input parameters. You can also include a route name in the expression, which lets you specify a route to use.
The following example shows how to use the RouteValue expression.
<asp:Label ID="Label1" runat="server" Text="<%$RouteValue:SearchTerm%>" />
When the page that contains this control runs, the value "scott" is displayed in the label.
The RouteValue expression makes it very simple to use route data in markup, and it avoids having to work with the more complex Page.RouteData["x"] syntax in markup.
Posted in: asp.net | Tags: asp.net asp.net 4.0 webform web application routing web form