为什么我不能使用EF 6 Code First为用户播种？

Question

就像标题所说，我正在使用Entity Framework 6.当我调用Update-Database时，种子方法失败：

SimpleMembershipProvider userMgr = new SimpleMembershipProvider();

if (WebSecurity.Initialized)
{
   if (userMgr.GetUser("administrator", false) == null) //--> Throws the exception
   {
      userMgr.CreateUserAndAccount("administrator", "password", false, null)
      ...
   }
}

抛出的异常：

System.InvalidOperationException: You must call the "WebSecurity.InitializeDatabaseConnection" method before you call any other method of the "WebSecurity" class. This call should be placed in an _AppStart.cshtml file in the root of your site.
   at WebMatrix.WebData.SimpleMembershipProvider.get_PreviousProvider()
   at WebMatrix.WebData.SimpleMembershipProvider.GetUser(String username, Boolean userIsOnline)
   at SomeProject.Migrations.Configuration.Seed(SomeProjectDB context) in c:\Users\Me\Documents\Visual Studio 2013\Projects\SomeProject\SomeProject 2.0\Migrations\Configuration.cs:line 73
   ...