User686339638 posted
My linq query works pretty good until i get to group by. I took a PluralSight class and it said that Linq can end in a Group By clause or a Select clause. However, in my VB.NET project, if i put Group By, it tells me "into is expected." These are very
simple queries. I'm able to get it to work, but... I have to use syntax that I don't understand. The PluralSight course was on C# but I've seen queries online that uses the same query syntax that I'm using.
Here is the object I created to test linq out.
Public Class Author
Private m_name As String
Private m_age As Short
Private title As String
Private mvp As Boolean
Private pubdate As DateTime
Private m_city As String
Public Sub New(name As String, age As Short, title As String, mvp As Boolean, pubdate As DateTime, city As String)
Me.m_name = name
Me.m_age = age
Me.title = title
Me.mvp = mvp
Me.pubdate = pubdate
Me.m_city = city
End Sub
Public Property Name() As String
Get
Return m_name
End Get
Set(value As String)
m_name = value
End Set
End Property
Public Property Age() As Short
Get
Return m_age
End Get
Set(value As Short)
m_age = value
End Set
End Property
Public Property BookTitle() As String
Get
Return title
End Get
Set(value As String)
title = value
End Set
End Property
Public Property IsMVP() As Boolean
Get
Return mvp
End Get
Set(value As Boolean)
mvp = value
End Set
End Property
Public Property PublishedDate() As DateTime
Get
Return pubdate
End Get
Set(value As DateTime)
pubdate = value
End Set
End Property
Public Property City() As String
Get
Return m_city
End Get
Set(value As String)
m_city = value
End Set
End Property
End Class
Afterwards I instantiate several objects and then try to create a Linq query.
Dim AuthorList As New List(Of Author)()
AuthorList.Add(New Author("Mahesh Chand", 35, "A Prorammer's Guide to ADO.NET", True, New DateTime(2003, 7, 10), "Mobile"))
AuthorList.Add(New Author("Neel Beniwal", 18, "Graphics Development with C#", False, New DateTime(2010, 2, 22), "Mobile"))
AuthorList.Add(New Author("Praveen Kumar", 28, "Mastering WCF", True, New DateTime(2012, 1, 1), "Mobile"))
AuthorList.Add(New Author("Mahesh Chand", 35, "Graphics Programming with GDI+", True, New DateTime(2008, 1, 20), "Mobile"))
AuthorList.Add(New Author("Raj Kumar", 30, "Building Creative Systems", False, New DateTime(2011, 6, 3), "Mobile"))
AuthorList.Add(New Author("Mahesh Patel", 35, "A Prorammer's Guide to ADO.NET", True, New DateTime(2003, 7, 10), "Atlanta"))
AuthorList.Add(New Author("Neel Patel", 18, "Graphics Development with C#", False, New DateTime(2010, 2, 22), "Atlanta"))
AuthorList.Add(New Author("Praveen Patel", 28, "Mastering WCF", True, New DateTime(2012, 1, 1), "Atlanta"))
AuthorList.Add(New Author("Mahesh Patel", 35, "Graphics Programming with GDI+", True, New DateTime(2008, 1, 20), "Pensacola"))
AuthorList.Add(New Author("Raj Patel", 30, "Building Creative Systems", False, New DateTime(2011, 6, 3), "Pensacola"))
'These two queries work with no problems:
Dim PeopleOfAtlanta = (From author In AuthorList
Where author.City = "Atlanta"
Select author).ToList
Dim PeopleNames = (From author In AuthorList
Where author.City = "Atlanta"
Select author.Name).ToList
'These two queries do not work:
Dim People = (From author In AuthorList
Group By author.City).ToList
Dim People2 = (From author In AuthorList
Group author By author.City).ToList
'This gives me the error: "into is expected."
'If I add into and put a group name afterward, it will add parenthesis to the end. For example:
Dim People = (From author In AuthorList
Group By author.City Into authorGroups()).ToList
'If i add a select statement was I was told during the PluralSight course (basically PluralSight said that if i add an INTO clause,
'i will need a select
'VS still adds parenthesis at the end of the into clause.
Dim People = (From author In AuthorList
Group By author.City Into authorGroups()
Select authorGroups).ToList
'In addition to this, Visual Studio gives me red squeakly lines in Solution Explore. The error message I'm getting is "Definition of method
'authorGroups is not accessible in this context."
' The only thing I can get to work are the following:
Dim People = (From author In AuthorList
Group By author.City).ToList
Into AuthorsByCity = Group).ToList
' I don't understand why I need the into statement or set it equal to Group. I don't understand this syntax it seems counter-intuitive.
'Thanks very much!
