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| Public Class MainForm
Private db As New CoursesClassesDataContext
Private Sub MainForm_Load(sender As Object, e As System.EventArgs) Handles Me.Load
Dim query = From aStudent In db.Students
Select aStudent.Id, aStudent.LastName, aStudent.Status,
aStudent.Major,
'**** Courses = aStudent.courses.count()********
Order By Id
DgvStudents.DataSource = query
End Sub
Private Sub dgvStudents_SelectionChanged() Handles DgvStudents.SelectionChanged
If dgvStudents.SelectedRows.Count = 0 Then Return
Dim studentId As Short = CShort(dgvStudents.SelectedRows(0).Cells(0).Value)
' This nested query is required in order to limit the columns appearing
' in the Courses grid.
dgvCourses.DataSource = From aCourse In (From aCourse In db.Courses
Select aCourse Where aCourse.Student_Id = studentId
Order By aCourse.Id)
Select aCourse.Id, aCourse.Credits, aCourse.Grade
'experiment with column formats
dgvCourses.Columns(1).DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter
With dgvCourses.Columns(2).DefaultCellStyle
.Format = "n"
.Alignment = DataGridViewContentAlignment.MiddleCenter
End With
End Sub
End Class |
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