Routing

Every page in DotVVM needs to be registered in the route table. DotVVM doesn't allow visiting a page just by putting its path in the URL.

The routes are configured in the DotvvmStartup class in the Configure method.

To separate the configuration options, the default project templates contain ConfigureControls, ConfigureRoutes and ConfigureResources methods, which are called from the Configure method. But you can use any structure you like, the only requirement is that the Configure method performs all the configuration actions.

Registering Routes One By One

In simple web apps, you can register each route individually using the following code snippet:

config.RouteTable.Add("Page", "my/page/url", "Views/page.dothtml", new { });

• The first argument is the name of the route. You'll need it when you do redirects or generate a hyperlink that navigates the user to this page. This name is not displayed anywhere, it is only a string which identifies the route in your code.

• The second argument is the route URL. It can contain route parameters (e.g. "product-detail/{ProductId}") which you can retrieve in the viewmodel when the page is loaded. For the default page, you can use "" as the route URL.

• The third argument is the location of the .dothtml file which will be used to handle the request. Because the file doesn|t have to be in the Views folder, you need to pass an application relative path including the Views folder name: Views/page.dothtml.

• The fourth argument (optional) specifies default values for route parameters. If the parameter value is not specified in the URL, the value from this object will be used. You can pass an anonymous object with property names that correspond with the route parameter names, or IDictionary<string, object>.

If you need to register a route which should not be treated as .dothtml file, e.g. if you need a handler that serves files, generates RSS feeds or anything like that, you can declare a custom presenter and specify a method, that creates an instance of it, as the fifth parameter.

If you have a larger project, you may want to use conventions to auto-discover routes instead of registering them one by one.

Route Parameters

Consider the following example. We need to create a page that can create a new customer, or display its details and allow to modify them.

In the first case, the URL is admin/customer. There is no customer ID, because we are creating a new one.

In the second case, the URL contains the ID of the customer we want to edit, e.g. admin/customer/3.

We can cover both cases using a single route. Its registration will look like this:

config.RouteTable.Add("AdminCustomer", "admin/customer/{Id}", "Views/admin/customer.dothtml", new { Id = 0 });

Notice that the route contains the parameter {Id}. Also, the fourth argument says that if the parameter is not present, its value should be 0.

In the viewmodel of the page, we can then access the value of the route parameter using the following code:

var customerId = Convert.ToInt32(Context.Parameters["Id"]);
if (customerId == 0) 
{
    // new customer
} 
else 
{
    // existing customer
}

We can also make the parameter optional (without the default value):

config.RouteTable.Add("AdminCustomer", "admin/customer/{Id?}", "Views/admin/customer.dothtml");

In that case, we need to check, whether the parameter is present in the URL:

if (!Context.Parameters.ContainsKey("Id")) 
{
    // new customer
}
else 
{
    // existing customer
    var customerId = Convert.ToInt32(Context.Parameters["Id"]);
}

Route Constraints

Additionally, we can use the route parameter constraints:

config.RouteTable.Add("AdminCustomer", "admin/customer/{Id:int}", "Views/admin/customer.dothtml", new { Id = 0 });

Notice the {Id:int} parameter, which says that the route will be matched only if the Id is an integer value.

DotVVM supports the following route constraints:

• alpha - alphabetic characters
• bool - true / false value
• decimal - decimal values with . decimal point symbol
• double - double values with . decimal point symbol
• float - float values with . decimal point symbol
• guid - a Guid value
• int - any integer number
• posint- a positive integer number (or zero)
• length(x) - any value with length of x characters
• long - any long integer number
• max(x) - any double value with . decimal point symbol that is less than x
• min(x) - any double value with . decimal point symbol that is greater than x
• range(x, y) - any double value with . decimal point symbol that is between x and y
• maxlength(x) - any value with length of x characters or less
• minlength(x) - any value with length of x characters or more
• regex(x) - any value that matches the regular expression x

You can also define your own route constraints by creating a class that implements the IRouteParameterConstraint interface. These custom constraints can be registered using this syntax in the DotvvmStartup file:

config.RouteConstraints.Add("customConstraint", new MyRouteConstraint());