System.Web.ClientServices.Providers contains client service providers that support remote access to the Microsoft Ajax authentication, roles, and profile services.
Today we will be looking at a common use case and solve it using client application services. We have a remote website containing the default ASP.NET membership provider and we need to access it from another website in order to log on a remote user.
In order to enable client application services in the remote site we need to change the web.config

<system.web.extensions>
<scripting>
	<webServices>
		<authenticationService enabled="true" requireSSL="false" />
		<profileService enabled="true" />
		<roleService enabled="true" />
	</webServices>
</scripting>
</system.web.extensions>

In our local website we need to define the remote authentication service

<membership defaultProvider="ClientAuthenticationMembershipProvider" userIsOnlineTimeWindow="120">
	<providers>
		<clear />
		<add name="ClientAuthenticationMembershipProvider" type="System.Web.ClientServices.Providers.ClientFormsAuthenticationMembershipProvider, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" serviceUri="http://www.myremotesite.com/AppServices/Authentication_JSON_AppService.axd" credentialsProvider="" />
	</providers>
</membership>
<roleManager enabled="true" cacheRolesInCookie="false" cookieTimeout="30" cookieRequireSSL="false" cookieSlidingExpiration="true" cookieProtection="All" defaultProvider="ClientRoleProvider" createPersistentCookie="false" maxCachedResults="25">
	<providers>
		<clear />
		<add name="ClientRoleProvider" type="System.Web.ClientServices.Providers.ClientRoleProvider, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" serviceUri="http://www.myremotesite.com/AppServices/Role_JSON_AppService.axd" cacheTimeout="86400" />
	</providers>
</roleManager>

In order to validate user credentials and log the remote user to our local website we need to use ClientFormsAuthenticationMembershipProvider

public static void ValidateUser(string userName, string password)
{
	try
	{
              ClientFormsAuthenticationMembershipProvider provider = (ClientFormsAuthenticationMembershipProvider)System.Web.Security.Membership.Providers["ClientAuthenticationMembershipProvider"];
		if (provider.ValidateUser(userName, password))
			FormsAuthentication.RedirectFromLoginPage(userName, true);
	}
	catch (WebException e)
	{
		throw new BusinessLayerException("Unable to access the remote service.", e);
	}
}

Now the remote user is logged into the local system. Client Application Services was initially created to assist desktop applications with remote authentication, but, will work great with websites too.