Route.Constraints Property (System.Web.Routing)

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.NET Framework Class Library

Route.Constraints Property

Gets or sets a dictionary of expressions that specify valid values for a URL parameter.

Namespace: System.Web.Routing
Assembly: System.Web (in System.Web.dll)

Syntax

Visual Basic

Public Property Constraints As RouteValueDictionary
	Get
	Set

public RouteValueDictionary Constraints { get; set; }

Visual C++

public:
property RouteValueDictionary^ Constraints {
	RouteValueDictionary^ get ();
	void set (RouteValueDictionary^ value);
}

member Constraints : RouteValueDictionary with get, set

Property Value

Type: System.Web.Routing.RouteValueDictionary
An object that contains the parameter names and expressions.

Remarks

The Constraints property enables you to limit acceptable values for a URL parameter that is processed by a route. You assign a RouteValueDictionary object to the Constraints property. Each element in the RouteValueDictionary object contains the name of a parameter and one of the following:

A string that defines a regular expression. The regular expression is case-insensitive.
An object that implements the IRouteConstraint interface and that includes a Match method.

The HttpMethodConstraint class implements the IRouteConstraint interface. You can include an instance of the HttpMethodConstraint class as a constraint to specify which HTTP verbs are acceptable for the route.

Examples

The following example shows how to create a Route object and set the Constraints, DataTokens, and Defaults properties.

Visual Basic


Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
    RegisterRoutes(RouteTable.Routes)
End Sub

Shared Sub RegisterRoutes(ByVal routes As RouteCollection)
    Dim urlPattern As String
    Dim reportRoute As Route

    urlPattern = "{locale}/{year}"

    reportRoute = New Route(urlPattern, New ReportRouteHandler)
    reportRoute.Defaults = New RouteValueDictionary(New With {.locale = "en-US", .year = DateTime.Now.Year.ToString()})
    reportRoute.Constraints = New RouteValueDictionary(New With {.locale = "[a-z]{2}-[a-z]{2}", .year = "\d{4}"})
    reportRoute.DataTokens = New RouteValueDictionary(New With {.format = "short"})

    routes.Add(reportRoute)
End Sub


void Application_Start(object sender, EventArgs e) 
{
    RegisterRoutes(RouteTable.Routes);
}

public static void RegisterRoutes(RouteCollection routes)
{
    Route reportRoute = new Route("{locale}/{year}", new ReportRouteHandler());
    reportRoute.Defaults = new RouteValueDictionary { { "locale", "en-US" }, { "year", DateTime.Now.Year.ToString() } };
    reportRoute.Constraints = new RouteValueDictionary { { "locale", "[a-z]{2}-[a-z]{2}" }, { "year", @"\d{4}" } };
    reportRoute.DataTokens = new RouteValueDictionary { { "format", "short" } };
    routes.Add(reportRoute);
}

The following example shows a Route object whose Constraints property contains a parameter named httpMethod with an instance of the HttpMethodConstraint class for the value.

Visual Basic


Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
    RegisterRoutes(RouteTable.Routes)
End Sub

Shared Sub RegisterRoutes(ByVal routes As RouteCollection)
    Dim urlPattern As String
    Dim reportRoute As Route
    Dim allowedMethods() As String = {"GET", "POST"}
    Dim methodConstraints As HttpMethodConstraint  

    methodConstraints = New HttpMethodConstraint(allowedMethods)

    Dim constraintValues = New With {.httpMethod = methodConstraints}

    urlPattern = "{locale}/{year}"

    reportRoute = New Route(urlPattern, New ReportRouteHandler)
    reportRoute.Constraints = New RouteValueDictionary(constraintValues)

    routes.Add(reportRoute)
End Sub


void Application_Start(object sender, EventArgs e) 
{
    RegisterRoutes(RouteTable.Routes);
}

public static void RegisterRoutes(RouteCollection routes)
{
    string[] allowedMethods = { "GET", "POST" };
    HttpMethodConstraint methodConstraints = new HttpMethodConstraint(allowedMethods);

    Route reportRoute = new Route("{locale}/{year}", new ReportRouteHandler());
    reportRoute.Constraints = new RouteValueDictionary { { "httpMethod", methodConstraints } };

    routes.Add(reportRoute);
}

Version Information

.NET Framework

Supported in: 4, 3.5 SP1

Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Reference

Route Class

System.Web.Routing Namespace

Other Resources

ASP.NET Routing