To call this method, the "Membership.Provider" property must be an instance of "ExtendedMembershipProvider"

Try setting the following up in your web.config within the <system.web> node:

    <roleManager enabled="true" defaultProvider="SimpleRoleProvider">        <providers>            <clear />            <add name="SimpleRoleProvider" type="WebMatrix.WebData.SimpleRoleProvider, WebMatrix.WebData" />        </providers>    </roleManager>    <membership defaultProvider="SimpleMembershipProvider">        <providers>            <clear />            <add name="SimpleMembershipProvider" type="WebMatrix.WebData.SimpleMembershipProvider, WebMatrix.WebData" />        </providers>    </membership>    <sessionState mode="InProc" customProvider="DefaultSessionProvider">        <providers>            <add name="DefaultSessionProvider" type="System.Web.Providers.DefaultSessionStateProvider, System.Web.Providers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" connectionStringName="DefaultConnection" />        </providers>    </sessionState>

Sounds like SimpleMembership isn't recognized when you go to use it.

Also, it may be worth including, the WebMatrix.webData library can be installed via NuGet:

PM> Install-Package Microsoft.AspNet.WebPages.WebData

Try to change the Login function under AccountController.cs

        //    // POST: /Account/Login    [AllowAnonymous]    [HttpPost]    public ActionResult Login(LoginModel model, string returnUrl)    {        if (ModelState.IsValid)        {            if (Membership.ValidateUser(model.UserName, model.Password))            {                FormsAuthentication.SetAuthCookie(model.UserName, model.RememberMe);                if (Url.IsLocalUrl(returnUrl))                {                    return Redirect(returnUrl);                }                else                {                    return RedirectToAction("Index", "Home");                }            }            else            {                ModelState.AddModelError("", "The user name or password provided is incorrect.");            }        }        // If we got this far, something failed, redisplay form        return View(model);    }

Did steps above but that didn't help. What helped was changing web.config:

      <dependentAssembly>    <assemblyIdentity name="WebMatrix.Data" publicKeyToken="31bf3856ad364e35" culture="neutral" />    <bindingRedirect oldVersion="0.0.0.0-3.1.0.0" newVersion="3.0.0.0" />  </dependentAssembly>          <dependentAssembly>    <assemblyIdentity name="WebMatrix.WebData" publicKeyToken="31bf3856ad364e35" culture="neutral" />    <bindingRedirect oldVersion="0.0.0.0-3.1.0.0" newVersion="3.0.0.0" />  </dependentAssembly>