C# 4 and .NET 4

1250 ❘ ChaPTer 42 Asp.net dynAmic dAtA And mvc
Alternatively, you can extract parameters by name as they are indexed in the collection; for example:
string parameterValue = Page.RouteData.Values["pathparameter"] as string;
expression Builders
There are two expression builders that you can use in ASP.NET markup files to extract and use route
parameter values: RouteValue and RouteUrl.
RouteValue can be used inline to output the value of a parameter, as follows:
For example, in the PCSRoutingDemo web site, the Target.aspx file includes the following line of markup code:
targetparameter =
code snippet PCSRoutingDemo/Target.aspx
This sets the Text property of a Label control to the value of the targetparameter parameter.
RouteUrl is used to construct URLs to match a route. This is a great feature when you are putting links in
your ASP.NET code, as a URL created in this way will change if the route definition ever changes. To use
this expression builder, you use markup inline as follows:
You can include more than one parameter by separating name/value pairs with commas. The expression
builder will attempt to match the parameters you specify to a route by the names of the parameters you use.
In some cases, you might have more than one route that uses the same parameters, in which case you can
identify the specific route to use by name as follows:
In PCSRoutingDemo, there are two separate links in the master page, one of which uses this expression builder:
Navigation with routing
Navigation with routing and expression builder
code snippet PCSRoutingDemo/MasterPage.master
The second version of this link shows the best way to include links in your markup, as it allows you to
change the route specification later, as noted above.
Data Query Parameters
Another way to use route parameters in your code is to supply them directly to data queries. This technique
enables you to fetch data from a database directly from markup code, rather than having to extract
parameter values and use them in the code-behind.
To do this, you use an in the parameters for a query. For example, you could use
the following in an data source: