This documentation is archived and is not being maintained.

HostNameComparisonMode Enumeration

Specifies how the host name should be used in URI comparisons when dispatching an incoming message to a service endpoint.

Namespace:  System.ServiceModel
Assembly:  System.ServiceModel (in System.ServiceModel.dll)

public enum HostNameComparisonMode

Member nameDescription
StrongWildcardIgnores the hostname when dispatching incoming messages to this endpoint. This is the default value.
ExactUses the hostname when dispatching incoming messages to this endpoint, if no strong match was found.
WeakWildcardIf no strong or exact match was found, ignores the hostname when matching.

The value is used to specify the URI matching rules used by transports such as HTTP, Net.Tcp, and Net.Pipe when dispatching incoming messages. Configure the value of the HostNameComparisonMode for a standard binding using one of the preceding transports, such as BasicHttpBinding, using the corresponding HostNameComparisonMode property. Configure the value of the HostNameComparisonMode for a binding element using one of the preceding transports, such as HttpTransportBindingElement, using the corresponding HostNameComparisonMode property.

Each value of the HostNameComparisonMode corresponds to a specific type of matching rule. The sequence of matching rules attempted is always ordered as follows:

  1. StrongWildcard()

  2. Exact()

  3. WeakWildcard()

The first value, StrongWildcard(), ignores the host name when matching and it takes the highest precedence of the three different matching modes. It is the default value for a system-provided binding or binding element. This indicates that a service endpoint can be reached using any valid host name. For example, if MyService is hosted using http://localhost/MyService, it is still reachable using because the (presumably valid) host name, "", is ignored. Note that the port is a wildcard here as well.

The second value, Exact(), requires that an exact match is found with the URI specified, including the hostname, if no strong match is found. This mode, for example, does not perform equivalence between short hostnames and fully-qualified domain names. This allows hostnames to be used as match criteria in the scenarios where multiple hosts are assigned a single IP address and it enables different services to be hosted on the same machine with distinct endpoints. Note that the port is a wildcard here as well.

The third value, WeakWildcard(), matches by ignoring the hostname if no strong or exact match was found. The behavior is the same as for StrongWildcard other than the order of matching: it runs after the strong and exact bindings have been tried.


These values have no effect when used inside of the Internet Information Services (IIS) or Windows Process Activation Service (WAS) hosting environment. In those cases, uses whatever hostname comparison mode is provided by the IIS Web Site hosting the services.

The following is an example of how to set StrongWildcard() value in a service side configuration file.

      <endpoint address="http://localhost:8000/UESamples/HelloService"
                contract="UE.Samples.ISayHello" />
      <endpoint contract="IMetadataExchange" binding="mexHttpBinding" address="mex" />

      <binding name="Binding1" 

      <behavior name="HelloServiceBehavior">
        <serviceMetadata httpGetEnabled="true" />


Here is a basic service and client that use the preceding configuration file.

public interface ISayHello
    string SayHello();

public class HelloService : ISayHello
    public string SayHello()
        return "Hello, WCF!";

// Open up a channel factory on a client application.
ChannelFactory<ISayHello> factory = new ChannelFactory<ISayHello>("BasicHttpBinding_ISayHello");

// Both of these contracts work (provided both hostnames are valid) because
// the binding configuration is set to hostNameComparisonMode="StrongWildcard".

ISayHello channel = factory.CreateChannel(new EndpointAddress("http://localhost:8000/UESamples/HelloService"));
ISayHello channel2 = factory.CreateChannel(new EndpointAddress("http://machineName/UESamples/HelloService"));


Console.WriteLine("Press <ENTER> to terminate client.");

.NET Framework

Supported in: 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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.