Lambda property value selector used in lambda expression - vb.net

Question

I sometimes find myself writing two versions of the same function that gets a count of members where one of several properties have a particular value. I've been looking at func and other examples to see if I could write a single function to do a count where a value matches one of several properties of an object. Feels like there should be a way...
Module Test
Private _students As New List(Of Student)
Sub Main()
_students.Add(New Student(1, "Stephen"))
_students.Add(New Student(2, "Jenny"))
' I'd like to replace the following lines...
Console.WriteLine(GetCountByID(1))
Console.WriteLine(GetCountByName("Stephen"))
' with a single function that could be used like below.
'Console.WriteLine(GetCountByType(1, Student.ID))
'Console.WriteLine(GetCountByType("Stephen", Student.Name))
Console.ReadLine()
End Sub
Public Function GetCountByID(ByVal id As Integer) As Integer
Return _students.Where(Function(s) s.ID = id).ToList.Count
End Function
Public Function GetCountByName(ByVal name As String) As Integer
Return _students.Where(Function(s) s.Name = name).ToList.Count
End Function
' I know this is wrong below but I'm just writing it like I'm thinking about it in my head
'Public Function GetCountByType(ByVal value As Object, selectorProperty As Func(Of Student)) As Integer
' Return _students.Where(Function(s) s.selectorProperty = value).ToList.Count
'End Function
Public Class Student
Public Property ID As Integer
Public Property Name As String
Public Sub New(ByVal id As Integer, ByVal name As String)
Me.ID = id
Me.Name = name
End Sub
End Class
End Module

Answer 1

You are along the right lines but your Func needed to return an object.
However it would be better to make it generic instead, the type needs to be of type IComparable so you can check for equality against the target value.
Public Function GetCountBy(Of T As IComparable)(selector As Func(Of Student, T), value As T) As Integer
Return _students.Where(Function(s) selector(s).CompareTo(value) = 0).Count()
End Function
Console.WriteLine(GetCountBy(Function(s) s.ID, 1))
Console.WriteLine(GetCountBy(Function(s) s.Name, "Stephen"))
p.s. your calls to ToList() are unnecessary
But once you have gone this far you might as well just pass in the complete predicate instead of a selector function and a value
Public Function CountWhere(predicate As Func(Of Student, Boolean))
Return _students.Where(predicate).Count()
End Function
Console.WriteLine(CountWhere(Function(s) s.ID = 1))
You can generalise this even further so it applies to any collection rather than just students, and make it an extension function if you wish
Public Function CountWhere(Of T)(coll As IEnumerable(Of T), predicate As Func(Of T, Boolean))
Return coll.Where(predicate).Count()
End Function
Console.WriteLine(CountWhere(_students, Function(s) s.ID = 1))