Add/Update list in database using Entity framework 6

The Entity Framework way to update is to to Context.Entry([your object]).State = System.Data.Entity.EntityState.Modified; providing that the object is of the right type.

public Boolean Add(QuestionBank AddQuetionBankData)
{

    bool flag = false;

    var question = this.MapToQuestion(AddQuetionBankData); //map the input to the EF Type Question
    var anwer = this.MapToAnswer(AddQuetionBankData); //map the input to the EF Type Answer

    var isQuetionBankPresent = _QuestionBankRepository.GetAll(p => p.Text == AddQuetionBankData.Text && p.Standard == AddQuetionBankData.Standard && p.Chapter == AddQuetionBankData.Chapter).FirstOrDefault<QuestionBank>();
    if (isQuetionBankPresent != null)
    {
        _context.Entry(question).State = EntityState.Modified;
        _context.Entry(answer).State = EntityState.Modified;
        /* Add the data in Question and Answer tables  */
        flag = false;
    }
    else
    {
        _context.Entry(question).State = EntityState.Modified;
        _context.Entry(answer).State = EntityState.Modified;
        _context.Entry(AddQuetionBankData).State = EntityState.Modified;
        /* Add the data in all three tables  */
        flag = true;
    }

    _context.SaveChanges();

    return flag;
}

private Question MapTo Question(QuestionBank q) //do this for Answers too
{
    var _q = _context.Question.Where(a=>a.Id == q.Id).SingleOrDefault();

    if(_q!=null)
    {
          _q.id = q.id; //this is already true
          _q.Title = q.Title;
          _q.QuestionText = q.Standard; //I guess
    }

    return _q;
 }

The EF updates the Entity (the class you pass to the method Entry()) accordingly to its Type.

Notice that the position of the SaveChanges(): it works like a stored procedure, you do all the updates and the SaveChanges() is like the SQL COMMIT command.

You should also wrap the SaveChanges in a try/catch to handle errors, and dispose the _context.

EDIT

This class has as dependency IRepository<Question>, IRepository<QuestionBank>, and IRepository<Answer>.

You should create an UpdateController(or PublishController or whatever) that gets the three dependencies in the constructor (better a Facade Service), and call the Add() method for each one of them.

If you access directly the raw Database object you could do like I did and use the Entry() method for each table.