ORDER BY NEWID in LINQ and bind to Repeater control - asp.net

Question

Morning,
I would like to know how to write the following SQL statement in LINQ.
SELECT TOP 6 * FROM Questions
ORDER BY NEWID()
I would also like to know, how i could bind this to a asp.net repeater control to display the 6 questions.
Many thanks :)

Answer 1

The Linq style would be
Questions.OrderBy(q=>Guid.NewGuid()).Take(6)
then you attach that to a repeater by setting its DataSource property to the above, and calling the DataBind method.

Answer 2

You would have to be able to invoke the NEWID() function to generate your random guids. To do so, you could take some hints here and first create a pseudo-method mapped to the NEWID() function on your data context.
[System.Data.Linq.Mapping.Function(Name="NEWID", IsComposable=true)]
public Guid NewId()
{
throw new NotImplementedException();
}
Once that is set, you could then write your query to use this function:
var query = dc.Questions
.OrderBy(question => dc.NewId())
.Take(6);
You can inspect the SQL query generated for this and it should match.

Answer 3

Questions.OrderBy(q=>Sql.NewGuid()).Take(6)
This will invoke the NEWID() in SQL statement.

Answer 4

(from db in context.Questions
order by Guid.NewGuid()
select db).Take(6);

Answer 5

I know answer is already selected, but still I'm adding my way to achieve this. Faced same situation today and tried couple of ways, used questions.OrderBy(q => Guid.NewGuid()).ToList() and couple of more suggestions. Later I thought to add a new field string RandomOrder in view model and assigned Guid.NewGuid().ToString() in loop and then used questions.OrderBy(i => i.RandomOrder).ToList() and this worked great.
I had requirement to shuffle questions if author selected option shuffleAlways while creating assessment. If not then sort on regular sorting order. Here is complete solution:
private List<AssessmentQuestionsViewModel> LoadAllQuestions(string assessmentId, bool shuffleQuestions)
{
List<AssessmentQuestionsViewModel> questions = new List<AssessmentQuestionsViewModel>();
var items = assessmentQuestionRepository.GetAll().Where(i => i.AssessmentId == assessmentId).ToList();
foreach (var item in items)
{
questions.Add(new AssessmentQuestionsViewModel
{
Id = item.Id,
AssessmentId = item.AssessmentId,
QuestionText = item.QuestionText,
HintText = item.HintText,
QuestionType = item.QuestionType,
MaxMarks = item.MaxMarks,
SortOrder = item.SortOrder,
RandomOrder = Guid.NewGuid().ToString(),
Answers = LoadAllAnswers(item.Id)
});
}
if (shuffleQuestions)
{
questions = questions.OrderBy(i => i.RandomOrder).ToList();
}
else
{
questions = questions.OrderBy(i => i.SortOrder).ToList();
}
return questions;
}
And this worked like charm. Hope this help others.

Answer 6

I assume you are using ORDER BY NEWID() as a way to select random data from your questions? If so, you should avoid using NEWID() (or it's LINQ equivalent), causes tons a new guid to be generated for every record in your table. On a large dataset, that's devestating.
Instead, see Linq Orderby random ThreadSafe for use in ASP.NET for an optimized solution to random sorts. Then just add a take operator and your set.
Random random = new Random();
int seed = random.Next();
var RandomQuestions = Questions.OrderBy( s => (~(s.Shuffle & seed)) & (s.Shuffle | seed)); // ^ seed);
return RandomQuestions.Take(6);