public async Task AddStudentsToClassAsync(Class class1, string[] studentsid)
{
if (class1 == null)
{
throw new ArgumentNullException("class1");
}
if (studentsid == null)
{
throw new ArgumentNullException("studentsid");
}
var list = new List <User>();
foreach (var student in studentsid)
{
var user = await UserStore.FindByIdAsync(student);
if (user != null)
{
list.Add(user);
}
}
await UserStore.AddStudentsToClassAsync(class1, list.ToArray());
}