在方法语法中选择C＃ - 返回匿名对象的集合

Question

I need to use Select operator to shape the data in a linq method syntax to return a collection of anonymous object with the Name and Age property.I know how to write a query syntax for achieving this but not able to do it with a method syntax

See the 2 pieces of code, 1st one works fine, 2nd getting error indicating Severity Code Description Project File Line Suppression State "Error CS1061 'IGrouping' does not contain a definition for 'StudentName' and no accessible extension method 'StudentName' accepting a first argument of type 'IGrouping' could be found (are you missing a using directive or an assembly reference?)"

var studentsGroupByStandard = from s in ObjectsMisc.studentList
                                          group s by s.StandardID into sg
                                          orderby sg.Key
                                          select new { sg.Key, sg };

var testS = ObjectsMisc
  .studentList
  .GroupBy(sg => sg.StandardID)
  .OrderBy(sg => sg.Key).Select(sg => new {
     Name = sg.StudentName,
     Age = s.Age
   });

so the 2nd piece generate a design error

Answer 1

The equivalent Method syntax for your first query would be

var testS = ObjectsMisc.studentList
    .GroupBy(s => s.StandardID)
    .OrderBy(sg => sg.Key)
    .Select(sg => new { sg.Key, sg})

However this does not select the StudentName and Age properties, but the whole student objects.

If your students have a StudentName and an Age property and you want to select these grouped by StandardId , it would be the following method syntax

var testS = ObjectsMisc.studentList
    .GroupBy(s => s.StandardID)
    .OrderBy(sg => sg.Key)
    .Select(sg => new { sg.Key, Students = sg.Select(s => new { s.StudentName, s.Age }) })