LINQ-to-SQL ComboBox Demo

'------------------------------------------------------------------------------------------
'           Notice of My Copyright and Intellectual Property Rights
'
' Any intellectual property contained within the program by Joseph L. Bolen remains the
' intellectual property of the Joseph L. Bolen. This means that no person may distribute,
' publish or provide such intellectual property to any other person or entity for any
' reason, commercial or otherwise, without the express written permission of Joseph L. Bolen.
'
'                 Copyright © 2015. All rights reserved.
'        All trademarks remain the property of their respective owners.
'-------------------------------------------------------------------------------------------
' Program Name:   LINQ-to-SQL ComboBox Demo
'
' Author:         Joseph L. Bolen
' Date Created:   Oct 2015
'
' Description:    Demonstrate various methods to code LINQ-to-SQL ComboBox
'                 initialization.
'
'                 Documentation is at:
'                   App's Visual Basic .NET code is at http://pastebin.com/gdZBAVKg
'-------------------------------------------------------------------------------------------

Public Class MainForm

    Private RegionBindingSource As New BindingSource

    Private Sub MainForm_Load(sender As Object, e As EventArgs) _
        Handles Me.Load

        ' Prevent event from firing until after the load of the ComboBox.
        RemoveHandler RegionDescriptionComboBox.SelectedIndexChanged,
            AddressOf RegionDescriptionComboBox_SelectedIndexChanged

        '' (1)-----------------------------------------------------------
        '' LINQ-to-SQL using a BindingSource and sorting the BindingSource.
        '' Preferred for a Master/Detail or Parent/Child table
        '' relationship.
        '' --------------------------------------------------------------
        'Using db As New NorthwindDataContext
        '    RegionBindingSource.DataSource = db.Regions
        'End Using

        'RegionBindingSource.Sort = "RegionDescription"

        'With RegionDescriptionComboBox
        '    .DisplayMember = "RegionDescription"
        '    .ValueMember = "RegionID"
        '    .DataSource = RegionBindingSource
        '    .SelectedIndex = -1
        'End With

        '' (2)-----------------------------------------------------------
        '' LINQ-to-SQL using a BindingSource and sorting in the query.
        '' Preferred for a Master/Detail or Parent/Child table
        '' relationship.
        '' --------------------------------------------------------------
        'Using db As New NorthwindDataContext
        '    Dim myQuery = From rec In db.Regions
        '                  Order By rec.RegionDescription
        '                  Select rec

        '    RegionBindingSource.DataSource = myQuery
        'End Using

        'With RegionDescriptionComboBox
        '    .DisplayMember = "RegionDescription"
        '    .ValueMember = "RegionID"
        '    .DataSource = RegionBindingSource
        '    .SelectedIndex = -1
        'End With

        '' (3)-----------------------------------------------------------
        '' LINQ-to-SQL w/o sorting. No BindingSource.
        '' --------------------------------------------------------------
        'Using db As New NorthwindDataContext
        '    With RegionDescriptionComboBox
        '        .DisplayMember = "RegionDescription"
        '        .ValueMember = "RegionID"
        '        .DataSource = db.Regions
        '        .SelectedIndex = -1
        '    End With
        'End Using

        '(4)------------------------------------------------------------
        ' LINQ-to-SQL using sorting. No BindingSource.
        ' --------------------------------------------------------------
        Using db As New NorthwindDataContext
            Dim myQuery = From rec In db.Regions
                          Order By rec.RegionDescription
                          Select rec

            With RegionDescriptionComboBox
                .DisplayMember = "RegionDescription"
                .ValueMember = "RegionID"
                .DataSource = myQuery
                .SelectedIndex = -1
            End With
        End Using

        AddHandler RegionDescriptionComboBox.SelectedIndexChanged,
            AddressOf RegionDescriptionComboBox_SelectedIndexChanged
    End Sub

    Private Sub RegionDescriptionComboBox_SelectedIndexChanged(sender As Object, e As EventArgs) _
        Handles RegionDescriptionComboBox.SelectedIndexChanged

        RegionIDResult.Text = RegionDescriptionComboBox.SelectedValue.ToString
    End Sub
End Class