Linq GroupBy Error

Question

Hello,

I have this code block in which I am trying to bind the QuestionText and Id to a dropdown box at runtime.  I have to group by the Question Text but keep getting an error on the DataBind() -

DataBinding: 'System.Linq.Lookup`2+Grouping[[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[<>f__AnonymousType0`2[[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Nullable`1[[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]], mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]], DeloitteDEXCharting, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' does not contain a property with the name 'QuestionText'.

What am I doing wrong?

            var results = from q in db.GetFilterQuestionsAndAnswers(templateId)
                          select new
                          {
                              QuestionText = q.QText,
                              QuestionId = q.QId
                          };
          
            ddFilterQuestion.DataSource = results.GroupBy(r => r.QuestionText);
            ddFilterQuestion.DataTextField = "QuestionText";
            ddFilterQuestion.DataValueField = "QuestionId";
            ddFilterQuestion.DataBind();

Answer 1

I found how to do it but seems like overkill.   Thought I could use a lamda expression to do it but this did the trick.   If you can use a lamda expression I would love to know how!

            var questions = from q in db.GetFilterQuestionsAndAnswers(templateId)
                            group q by new
                            {
                                QText = q.QText,
                                QId = q.QId
                            }
                                into grp
                                select new
                                {
                                    QuestionText = grp.Key.QText,
                                    QuestionId = grp.Key.QId
                                };

Answer 2

Hi Jason,

Here's the equivalent query using lambda expressions (I used LINQPad to convert it ):

var questions =
db.GetFilterQuestionsAndAnswers(templateId)
   .GroupBy (
      q => 
         new  
         {
            QText = q.No, 
            QId = q.Description
         }
   )
   .Select (
      grp => 
         new  
         {
            QuestionText = grp.Key.QText, 
            QuestionId = grp.Key.QId
         }
   );

However I would still prefer the non-lambda syntax that you posted in your second post since it is much easier to read.


Regards,

---

Syed Mehroz Alam
My Blog | My Articles

Answer 3

Thanks - I am using LinqPad as well.  How did you use to convert?

Answer 4

Hi Jason,

 

After querying the database using C# statements in LINQPad, please select the “λ” (Lambda Expressions) in the result window.  We will see the corresponding lambda syntax there.

 

 

Hope you have a nice day!

 

 

Best Regards,
Lingzhi Sun

---

Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.

Answer 5

Hi Jason,

 

Do you need any further assistance?  If so, please feel free to let me know.

Have a nice day!
 

 

Best Regards,
Lingzhi Sun

---

Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.

Answer 6

All set, thanks!