LINQ获得最高值和+ 1

Question

I'm newbie to LINQ. I will like to get know what's the highest value for 'Question Position' and i want increase it by 1 for new Question and save it into database from MVC 4 view.

My db data : (highest position value is 2)

====================
Question  | Position
====================
Q1        |     1
Q2        |     2

After added new Question : ( increment the highest position (2) + 1 )

====================
Question  | Position
====================
Q1        |     1
Q2        |     2
Q3        |     3

My Code :

var query =
                db.SURV_Question_Model
                .Where(r => r.Question_Survey_ID == viewModel.Survey_ID)
                .GroupBy(r => new { r.Question_Position })
                .Select(grp => grp.OrderByDescending(i => i.Question_Position).FirstOrDefault());

After i get the highest value from query, can i do something like below?

* int i = query.Question_Position + 1 ??? 

Appreciate your guidance.

Answer 1

You can use Max :

var maxId = db.SURV_Question_Model
              .Where(r => r.Question_Survey_ID == viewModel.Survey_ID)
              .Max(x => x.Position);

But, if there is not any record it will throw an exception. So, it will be better to change your code as:

var maxId = ...Max(x => (int?)x.Position) ?? 0;

Answer 2

You don't need the GorupBy method, this should be enough:

var maxId =
    db.SURV_Question_Model
    .Where(r => r.Question_Survey_ID == viewModel.Survey_ID)
    .OrderByDescending(x => x.Position)
    .FirstOrDefault());

I actually don't know the usage of the where condition, I left there anyway.