We have two existing website webA and webB. They use different custom membershipprovider and roleprovider. webA's user and role tables are in database A and webB's user and role tables are in database B. 

Now we are trying to use DotNetNuke for content management on both websites, ideally store the content management tables in a separate database, database C. What's the best way to accomplish this and utilize the existing custom MembershipProviders and RoleProviders?

Thanks,

Jason

Thanks for the reply. I think I should provide some details as how I solved (I hope) the problem. Hope it can help other people looking for an answer on the same question.

MembershipProvider is not a problem. I can just user Membership.Providers[ProviderName].ValidateUser. That's it.

For RoleProvider, there is a nice post here that explains how to set the RoleProviderName in a cookie and retrieve it later on. 

So my solution is:

1. Create a new custom RoleProvider, which will be used as the default RoleProvider for the DotNetNuke website, which may contain multiple portals.
2. Keep the definition for the DotNetNuke RoleProvider in web.config, but it's not the default anymore.
3. In my case, I am trying to integrate two websites. For each website, define a RoleProvider in web.config. 
4. Each website has its own login page. In the login button click event, set the cookie as describe in the above link.
5. In the new custom RoleProvider, read the RoleProviderName from the cookie, and get the RoleProvider from Roles.Providers[RoleProviderName] and overwrite each of the methods, such as GetRolesForUser, IsUserInRole.

Web.config roleManager:

<roleManager defaultProvider="DefaultRoleProvider" enabled="true" cacheRolesInCookie="true">
<providers>
        <add name="DefaultRoleProvider" type="MultiRoleProviderWebsite.DefaultRoleProvider" connectionStringName="dbConnStr" applicationName="Application0" />
        <add name="RoleProvider1" type="MultiRoleProviderWebsite.RoleProvider1" connectionStringName="dbConnStr" applicationName="Application1" />
<add name="RoleProvider2" type="MultiRoleProviderWebsite.RoleProvider2" connectionStringName="dbConnStr" applicationName="Application2"/>
</providers>
</roleManager>

public class DefaultRoleProvider : SqlRoleProvider
    {
        public DefaultRoleProvider()
        {
        }

        private RoleProvider Provider
        {
            get
            {
                string providerName = GetProviderName();
                RoleProvider provider = null;
                if (!string.IsNullOrEmpty(providerName))
                    provider = Roles.Providers[providerName];
                else
                    provider = Roles.Provider;

                return provider;
            }
        }

        public string CustomProviderName
        {
            get
            {
                return Provider.Name;
            }
        }

        public override string[] GetAllRoles()
        {
            return Provider.GetAllRoles();
        }

        public override bool RoleExists(string roleName)
        {
            return Provider.RoleExists(roleName);
        }

        public override string[] GetRolesForUser(string username)
        {
            return Provider.GetRolesForUser(username);
        }

        public override string[] GetUsersInRole(string roleName)
        {
            return Provider.GetUsersInRole(roleName);
        }

        public override bool IsUserInRole(string username, string roleName)
        {
            return Provider.IsUserInRole(username, roleName);
        }

        private string GetProviderName()
        {
            HttpCookie authCookie = HttpContext.Current.Request.Cookies["ANewCookie"];

            if (authCookie != null)
            {
                FormsAuthenticationTicket authTicket = FormsAuthentication.Decrypt(authCookie.Value);

                if (!string.IsNullOrEmpty(authTicket.UserData))
                {
                    string[] parts = authTicket.UserData.Split('=');

                    if (parts.Length == 2 && parts[0] == "Provider")
                    {
                        return parts[1];
                    }
                }
            }

            return "";
        }
    }