How to display only selected data in combo box at run time from database?

#Region "Imports"
 Imports System.Data.SqlClient
Imports System.Text

#End Region

Public Class StudentRecordForm

#Region "Record Types"
     Private Enum RecordType
        [NameType] = 0
        [GradeType]
    End Enum

#End Region

    Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
        Me.cboName.DataSource = Me.GetStudentNames(RecordType.NameType)
        Me.cboName.DisplayMember = "Record"
        Me.SetDefault(RecordType.NameType, "John")

        Me.cboGrades.DataSource = Me.GetStudentNames(RecordType.GradeType)
        Me.cboGrades.DisplayMember = "Record"
        Me.SetDefault(RecordType.GradeType, "A")
    End Sub

#Region "Data Source Assignment"
     Private Function GetStudentNames(ByVal type As RecordType) As ICollection(Of String)
        Dim returnList As ICollection(Of String) = New List(Of String)
        Dim queryString As New StringBuilder
        queryString.AppendLine("Select [Student_Data].[StudentRecords] As Record From [Student_Data]")
        Select Case type
            Case RecordType.NameType
                queryString.AppendLine(String.Format(My.Application.Culture, "Where [Student_Data].[StudentDetail] = '{0}'", "StudentName"))
            Case RecordType.GradeType
                queryString.AppendLine(String.Format(My.Application.Culture, "Where [Student_Data].[StudentDetail] = '{0}'", "StudentGrade"))
        End Select
        Using connection As IDbConnection = Me.GetConnection
            Using command As IDbCommand = connection.CreateCommand
                command.CommandTimeout = 0
                command.CommandType = CommandType.Text
                command.CommandText = queryString.ToString

                Using reader As IDataReader = command.ExecuteReader(CommandBehavior.SequentialAccess)
                    While (reader.Read)
                        returnList.Add(CStr(reader("Record")))
                    End While
                End Using
            End Using
        End Using
        Return returnList
    End Function

    Private Function GetConnection() As SqlConnection
        Dim connection As New SqlConnection
        Dim connectionString As New SqlConnectionStringBuilder
        Try
            connectionString.DataSource = "ADITY\SQLEXPRESS"
            connectionString.InitialCatalog = "BillingPro"
            connectionString.IntegratedSecurity = True
            connectionString.PersistSecurityInfo = False
            connection.ConnectionString = connectionString.ToString
            connection.Open()
        Catch sqlEx As SqlException
            MessageBox.Show(sqlEx.Message)
        Catch openEx As InvalidOperationException
            MessageBox.Show(openEx.Message)
        End Try
        Return connection
    End Function

#End Region

#Region "Set Default"
     Private Sub SetDefault(ByVal type As RecordType, ByVal defaultValue As String)
        Select Case type
            Case RecordType.NameType
                If (Me.cboName.Items.Count > 0) Then
                    Me.cboName.SelectedIndex = -1
                    For intIndex As Integer = 0 To Me.cboName.Items.Count - 1
                        If (String.Compare(defaultValue, Me.cboName.Items(intIndex).ToString, StringComparison.CurrentCultureIgnoreCase) = 0) Then
                            Me.cboName.SelectedIndex = intIndex
                            Exit For
                        End If
                    Next
                End If
            Case RecordType.GradeType
                If (Me.cboGrades.Items.Count > 0) Then
                    Me.cboGrades.SelectedIndex = -1
                    For intIndex As Integer = 0 To Me.cboGrades.Items.Count - 1
                        If (String.Compare(defaultValue, Me.cboGrades.Items(intIndex).ToString, StringComparison.CurrentCultureIgnoreCase) = 0) Then
                            Me.cboGrades.SelectedIndex = intIndex
                            Exit For
                        End If
                    Next
                End If
        End Select
    End Sub

#End Region

End Class