LINQ集团与C＃

Question

I have made a method in my Models class to call set of data from data base by below codes:

public IQueryable result(string username, string exam)
     {

        return (from result in idb.User_Exam_Question
                where (result.User_Tbl_email == username && result.Exam_Tbl_ID ==   Convert.ToInt32(exam))
                group result by result.category_tbl_ID into cat
                select cat);
    }

but I need to count the rows of each category . how should I change the above code to get my desirable output .

many thanks

Answer 1

If you want to return the count, just add .Count() :

public int result(string username, string exam)
{
    return (from result in idb.User_Exam_Question
            where (result.User_Tbl_email == username && result.Exam_Tbl_ID == Convert.ToInt32(exam))
            group result by result.category_tbl_ID into cat
            select cat).Count();
}

Or, if you want each sub-result as a count, you can do this:

public IQueryable result(string username, string exam)
{
    return from result in idb.User_Exam_Question
           where (result.User_Tbl_email == username && result.Exam_Tbl_ID == Convert.ToInt32(exam))
           group result by result.category_tbl_ID into cat
           select new
           {
               CatCount = cat.Count()
           } 
}

You can then do something like this:

result("username", "exam")[0].CatCount;
// returns the count of the first result of the query.

Answer 2

You can get the count directly from your cat !

public IQueryable result(string username, string exam)
     {

        return (from result in idb.User_Exam_Question
                where (result.User_Tbl_email == username && result.Exam_Tbl_ID ==   Convert.ToInt32(exam))
                group result by result.category_tbl_ID into cat
                select new { Group = cat , Count = cat.Count()  } );
    }