He seguido algunos tutoriales para la autenticación de API web con OWIN. La mayoría de estos tutoriales personalizan OAuthAuthorizationServerProvider. Sin embargo, cuando depuro "F11" no se alcanza la clase OAuthAuthorizationServerProvider

 private void ConfigureAuth(IAppBuilder app)
        {
            //
            app.UseCookieAuthentication(new CookieAuthenticationOptions()
            {


            });

            //
            app.UseExternalSignInCookie(Microsoft.AspNet.Identity.DefaultAuthenticationTypes.ExternalCookie);

            OAuthAuthorizationServerOptions authorizationServerOption = new OAuthAuthorizationServerOptions()
            {
                /*
                 * for demo only
                 * to enforce the Token retrieval over SSL (any non-https requests for requesting the Token will be denied)
                 * set AllowInsecureHttp = false
                */

               // AllowInsecureHttp = true,

                // Add token to the API dir
                //TokenEndpointPath = new PathString("/token"),

                //
                //Provider = new AWOAuthServerProvider(),

                // For test only 1 Day token expiry
                //AccessTokenExpireTimeSpan = TimeSpan.FromDays(1)

            };


            authorizationServerOption.AllowInsecureHttp         = true;
            authorizationServerOption.TokenEndpointPath         = new PathString("/token");
    /*break point*/
            authorizationServerOption.Provider                  = new AWOAuthServerProvider();
            authorizationServerOption.AccessTokenExpireTimeSpan = TimeSpan.FromDays(1);

            // Enable the application to use bearer tokens to authenticate users
            app.UseOAuthBearerTokens(authorizationServerOption);

            // Token Generation
            app.UseOAuthAuthorizationServer(authorizationServerOption);

            //Token Consumption
            app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions()
            {


            });

        }    

¿Cómo puedo usar o llamar al método al lado de la clase OAuthAuthorizationServerProvider?

 public class AWOAuthServerProvider : OAuthAuthorizationServerProvider
    {
        public override async Task ValidateClientAuthentication
            (OAuthValidateClientAuthenticationContext context)
        {
            await Task.FromResult(context.Validated());
        }

        public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext  context)
        {

            if (!ValidCredential(context.Password,context.UserName))
            {
                context.SetError("invalid_grant", "The user name or password is incorrect.");
                return;
            }


            var identity = new ClaimsIdentity(context.Options.AuthenticationType);
            identity.AddClaim(new Claim(ClaimTypes.Role, "user"));
            identity.AddClaim(new Claim("username", context.UserName));

         context.Validated(identity);

        }

Este es un método auxiliar para la credencial válida de Active Directory

         private bool ValidCredential (String password,String username)
                {
                    string[] NTId           = { "", "" };
                    string   netDomain      = "";
                    string   netUserName    = "";
                    bool     isValid        = false;

                    //
                    // context.OwinContext.Response.Headers.Add("Access-Control-Allow-Origin", new[] { "*" });


                    /*****************************************************************************************/
                    if (username.Equals(null) || username.Equals(""))
                    {
                        //Request client Network username
                        try
                        {
                            NTId = (HttpContext.Current.Request.LogonUserIdentity.Name)
                                                   .Replace(@"\\", @"\")
                                                   .Split('\\');
                        }
                        // error
                        catch (Exception e)
                        {
                            return false;
                        }
        }
 if (NTId.Length == 2)
                {
                    netDomain = NTId[0];
                    netUserName = NTId[1];
                }
     try
                {
                    using (PrincipalContext principalContext = new PrincipalContext(ContextType.Domain, netDomain))
                    {

                        isValid = principalContext.ValidateCredentials(netUserName, password);
                    }
                }
                // error 
                catch (Exception e)
                {
                    return false;
                }


                return isValid;
    }

Thinks